INDEX Sl. No.
CONTENT
AUTHOR
Page No.
Volume – I 1 2 3
4
5 6
Role of Various Departments to Improve Rail/Welds Reliability Improving the In-Service Reliability of Rails and Rail Welds Improving In-Service Reliability of Rails and Welds
Pradeep Kumar Garg,
Sr. Professor(Track)/IRICEN
B. K. Singh,
Sr. DEN/II/Dhanbad/EC Railway
1-16 17-45
V. K. Pandey,
Sr. DEN/C/Mughalsarai
Pawan Kumar,
47-58
Sr. DEN/1/Mughalsarai
Rajneesh Mathur,
Improving In-Service Reliability of Rails and Rail-Welds
CE/TP/ NFR
R. K. Das,
59-72
XEN/TMR/ NFR
Use of New Technology for Improved Service Reliability of Rails and Rail Welds Improving In-Service Reliability of Rails and Welds
Ajay Kumar,
ADEN/GLPT, NFR
Nitin Garg,
DEN/Spl.Works/Sealdah/ ER
73-88 89-96
S. K. Pandey,
7
Exe. Director/Track-I/RDSO
Improving the Reliability of A.T. Welds
Rajiv Kumar,
Director/Track/RDSO
97-110
A. K. Sharma,
ADE/Track/RDSO
8 9 10 11
Effect of Wheel Defects on Rail Fracture Rail Welding - The Managerial Solutions Improving the In-Service Reliability of Rails and Rail Welds In-Service Reliability of Welds: GMT Based Through Weld Renewal i
Nilmani,
Professor (Track)/IRICEN
K. Venkateswara Rao, GM/RITES/ SC
V. Harikrishna Reddy, ADEN/RU
111-131 133-158 159-170
N. K. Garg, CTE/WR
I. S. Rajput,
AEN (TM)/CCG
171-176
Sl. No.
CONTENT
AUTHOR
12
Rails and Rail Welds - Improving the In-Service Reliability
13
Improving the In-Service Reliability of Rails and Rail Weld Points & Crossing Laying and Maintenance
Page No.
J. C. Parihar,
OSD/Engg(HAG)/W.Rly/CCG
M. Badruddin,
177-182
Chem & met.Supdt/W.Rly/CCG
Dhananjay Singh, Sr. DEN/S/BCT
183-193
Volume – II 14
N. Aravindan,
Track Structure for Metro
Formerly AM/CE, Ministry of Railways
195-212
Vipul Kumar,
15
Ballastless Track an Overview and Developments in India
Executive Director/Track/ RDSO
Ashwani Kumar,
Director/Track/RDSO
213-229
Rituraj,
Deputy Director/Track/RDSO
16
17
Naresh Lalwani,
Selection of Ballastless Track for Indian Railways
Sr.Professor/Bridges/IRICEN
Pradeep Kumar garg,
231-253
Sr.Professor/Track/IRICEN
Ballastless Track Technologies Understanding the General Principles Behind Design, Features of Popular Systems, and Planning for Indian Conditions
Surendra Kumar Shrivastav, C..E/ S.C. Rly
Hansraj Sharma,
Dy Chief Manager / IT / East Coast Railway
255-266
Ashutosh Kumar Shukla, Dy .CE(Bridges) / ECR
18
Ballastless Track on Earthwork, Bridges and Tunnels - The Specific Problems Encountered and Various Considerations in its Design
ii
Pankaj Kumar Singh,
Sr. DEN/Co-ord /E.Rly/Asansol
267-279
Sl. No. 19 20 21 22 23 24
CONTENT
AUTHOR
Evolving Economical & Appropriate Design of Ballastless Track Ballastless Track Designs for Mainlines, Metros and at Washable Aprons Development of Appropriate Design of Ballastless Track for Bangalore Metro Rail Project Laying of Ballastless Track System in Pirpanjal Tunnel Construction of Washable Apron by Rheda 2000 Method Evolving Economical and Appropriate Design of Ballastless Track
D.K. Chandrakar, DY.CE/BR/I/C.R.
J. S. Mundrey ,
(Formerly Advisor, Civil Engineering, Railway Board)
S. P.Iyer,
Retd. CAO/CN
Vinod Kumar,
Dy.CE/C/N.Rly /Banihal
Page No. 281-294 295-318
319-342 343-363
S. S. Khongrymmai,
Sr.DEN/I/APDJ,/N.F.Rly
B. Chakraborty,
365-377
ADEN/HQ/APDJ,/N.F.Rly
Shiv Om Dwivedi,
Dy CE/Const./Design-1/N.Rly
379-398
S. Vijayakumaran,
25
Over View on Ballast Less Track in MRTS/Chennai
CAO/CN/MS
P. Kalimuthu, CE/MTP(R)/MS
399-418
R. Ravikumar,
Dy.CE/MTP(R)/MTMY
D. Anjaneyulu Reddy,
26
Rehabilitation of Washable Aprons using Accelerated Early High Strength Micro Concrete
Sr.DEN/Co-ord/SC/SCR
K. Mutyala Naidu,
DEN/Central/SC/SCR
419-433
D. Venkata Ramana, SSE/Works/HYB/SCR
27
28
Ballastless Track - Practical Difficulties in Laying & Maintenace
Precast Washable Apron on RTM Station - a Case Study
iii
Kaushal Kishore,
Chief Engr. (General)/WCR
J.N Verma,
435-447
Dy. CE (General)/WCR
A.M. Kaushal,
Dy.CE/(TM),Churchgate/W.Rly
Narendra Singh, ADEN /NW/ADI
449-456
Sl. No. 29
CONTENT
AUTHOR
Nagpur RRI Commissioning – A Pleasant Experience
Brijesh Dixit, DRM/NGP/C.R
Page No. 457-467
N. C. Sharda,
Dean, IRICEN/Pune
30
Critical Analysis of Performance of Various Lining Methods Available with Machine Tamping
Manoj Arora, Sr. Prof./Track-1/IRICEN Pawan Patil,
469-479
Dy.CE/TM, Bhusawal/ C.Rly.
D. V. B. Rao,
ADEN./TM, Bhusawal/C.Rly.
31 32 33 34 35
36
Improving Reliabilty of In-Service Rails - Alignment Rectification & Retention on Channel Sleepers on Bridges Polymers, Rail Corrosion Control by Fibres & Fibres in Concrete
P.V.N.Naidu,
Deep Screening of Yard Main Lines by BCM’s for Improving the InService Reliability of Rails and Welds
B. Krishna Reddy,
India Needs More DMRCS or More MRVCS? Improving the In-Service Reliability of Rails and Rail Weld Problem of Corrosion & Breaking of Plate Screw and its Remedy
K Venkateswara Rao,
Installation of Ballastless Track Turn Out in Bangalore Metro Rail Project
iv
Principal / DCETC/BZA
G.Kiran Babu,
481-491
Instructor/DCETC/BZA
M. Suyambulingam,
CE/TMC/S.Rly.
Sr. DEN/S.C.Railway
T. Anil Kumar,
493-504 505-512
ADEN/S.C.Railway GM/RITES/SC
A. A. Pathan,
SSE(P.Way) /JAO
A.S. RAJAGOPAL, Rtd, Dy.CE/S.W.Rly V.N. SEETHARAMAN, Ex. JE/ P.Way/S.W.Rly
513-518
519-523
525-539
TRACK STRUCTURE FOR METRO N. Aravindan, (Formerly AM/CE, Ministry of Railways)
Synopsis: Metro Rails pass through densely populated areas and hence are mostly built with elevated viaduct structures and underground tunnels. Being Metro service, it shall be designed and constructed for less maintenance and hence the need for maintenance-less or less maintenance assets. Ballast-less track meets this requirement economically and hence has been the choice for Metro Track. Presently Ballast-less track is adopted mostly on empirical basis without detailed examination of the behavior of track and its supporting structure as a system. This paper details the Ballast-less Track structure design with suggestions for design criteria. 1. Ballast - less Track - a necessity for Metro Rail Ballast - not for hard support base. i.
Ballast bed provides required elasticity (track modulus) to track structure which effectively contains the stress in track components apart from providing comfortable ride. The elasticity is achieved by inter grain supports of ballast over very small contact areas. The extant of such support areas and resulting stress is a function of the elasticity of the medium on which the ballast layer rests. In case of hard support beds like concrete base the contact stress will be more than that obtained for a flexible base like earthen formation. High stress results in pulverization of ballast leading to loss of springiness (elasticity) faster on hard support beds leading to deterioration in ride quality and track geometry at a faster rate needing frequent maintenance. Tamping with track machines is normally the first course of action resorted to in such cases 195
which involves line occupation and associated costs. On bridges and tunnels working conditions are not conclusive for easy maintenance affecting productivity. ii.
Since pulverized particles contaminate ballast, elasticity of ballast bed will further reduce leading to more pulverization and poor retentively of track geometry calling for still frequent attentions till ballast is cleaned by shallow screening or deep screening. These activities over bridge decks and tunnels present additional problems with poor productivity which adds up to maintenance costs.
iii.
Harder ballast bed without timely deep screening results in component failures like sleeper/ Rail failure which affect throughput and adds to costs.
iv.
Clogged ballast bed especially in tunnels where there could be water seepage results in poorly drained ballast bed leading to further loss of its capacity to transmit loads effectively and call for urgent maintenance actions.
Alternative track support without ballast is therefore required for Metro track’s which is Ballast - less track. Ballast-less Track is ideal for Tunnels. v.
The influence of climatic elements like variation in rail temperature needs to be accounted for in design of track and supporting structures. Track in tunnel, for all practical purposes is insulated from these elements that will result in economics in design and maintenance compared to open formation and bridge deck. In case of bridge decks the relative differential expansion between welded rail and bridge girder will have to be considered and countered for.
196
vi.
Track maintenance operations in tunnel are more difficult adding to cost compared to open formation and bridge decks and hence adoption of BLT in tunnels helps to provide maintenance free and hindrance free track structure.
vii.
Shallow construction depth and a reduced profile for moving standard dimension saves cost for tunnels. Increased reliability, better stability, very low maintenance – practically maintenance free, higher speed potential, greater track availability for traffic are further advantages of BLT. Engineered noise and vibration control are possible with ballast-less track.
viii.
Difference in Capital cost of ballast-less track and ballasted track becomes in significant for tunnels whereas the life cycle cost of BLT is many times more than ballasted track.
Ballast-less Track is therefore the track structure for Tunnels.
2. Types of Ballast-less Track. Of various types of BLT available, the most commonly used are ‘Direct Fixation Types (DFT)’. 1. Plinth beam type; predominantly used over viaducts. 2. Slab types; predominantly used in tunnels and formations. Ballast-less track consists of Rails, Fastening systems (Track Frame), and a concrete member cast between the track frame and supporting civil structure. These types are constructed by keeping rails in final position supported with suitable frames capable of line and level adjustment. The rail seat assemblies are fixed to Rails and the concrete member (plinth beam or slab) is cast in such condition and allowed to harden. This type of construction is termed as top down construction. 197
Rail choice is governed by stress in rail due to axle load, speeds and LWR forces especially considering the interaction between track and supporting structures as well as maintenance and replacement requirements which is critical for metros. Fastening choice attains more importance considering the fact that fastenings apart from their usual role shall also fill in the requirement of ballast resilience. For a metro these two components become a choice from past performance in similar usage rather than design and are selected from what is readily available whereas the concrete member needs specific design. Ballast-less tracks whether Slab type or Plinth Type are supported on rigid supports; a rigid concrete layer of tunnels invert or a comparatively stiff (box) girders of viaducts. They are not subjected to flexure like normal Concrete sleepers of ballasted track. Hence their structural design is mainly checks for resistance against lateral and longitudinal forces developed by Rolling Stock due to Cant excess / deficiencies and tractive and / or braking efforts as well as interaction of CWR with their supporting structure to which they are integrally connected rather than vertical load transfer capability (flexure). The main requirement of this intermediate layer is facilitating attainment of correct Rail level over in correct supporting base levels. Major deviations in viaduct top / tunnel base level will have adverse effect on finished Rail levels which is un-acceptable at least at Stations. Therefore the design of BLT consist of, 1. Check for adequacy of integral connection (shear connectors) between the plinth / slab and its supporting structure; that is design for resisting longitudinal and lateral forces. This is important for Plinth type BLT than a slab type which is comparatively more stable and heavy. 2. Check for its capability to resist derailment forces and over turning moments imposed on derailment up-stands. As is well known, assessment of derailment forces is never precise and hence this can only be empirical and approximate. It may be 198
recalled that none of the track components are designed to resist derailment forces. Criteria for these checks are given in Appendix from which it may be seen that 'nominal' provisions for size of members and reinforcements are more than adequate. The main function of this intermediate layer between track frame and supporting civil structure is to provide a construction layer to achieve required line and level precision for Rails on the previously cast (imperfect) supporting structures. The design of BLT is therefore more of detailing than structural design. 3. System design While the design of Plinth beam or Slab supporting track frame are simple and nominal, what is more important in BLT design is the design of the whole 'System' consisting of Track and the supporting structure as well. The effect of expanding/ contracting girders against rigidly connected non moving track frame needs special examination. The interaction between Track and the supporting structure is more important than individual component design of Track beam/ slab. This applies to design of girders, bearings, piers and its foundations as well. Investigation for additional stress developed in both Track (Rails) and supporting structure (Girders/ bearings) is crucial. UIC Code 774-3 R provides a method for ballasted track with design curves and limiting values of additional stress and movements. Though they are not directly applicable ballast-less tracks, guidance can still be taken with approximations to check the effects. This analysis needs computer simulation and analysis for a stretch of viaduct and may need Rail Expansion devices at critical locations. Fastenings with lower longitudinal restraints can be allowed to be provided for a perdetermined length near moving ends of girders to minimise the ill effects of differential movement between Rail and supporting girders. It may be realized that curvatures of typical Metro tracks and the configuration of supporting girder spans and their bearings will not 199
meet the stipulations of LWR Manual of IR to lay CWR. However in every Metro this is a normal feature. The only compliance is to UIC 774-3R provisions which are not directly applicable. Detailed study for such a system and making provision for laying CWR in Metro needs to be done by IR with utmost urgency. 4. Parameters for Design of Ballast-less Track. A simulation study of the possible systems shall lay down criteria for following based on which ballast-less track design shall be performed. This is essential for viaduct structures. 1. Viaduct configuration in terms of girder types, spans and pier types and their foundation shall be kept in view to meet the requirement of Track - Structure interactions in the initial planning itself. For this guidelines need to be provided based on simulation studies. 2. Locations for turnouts and piers (with respect to girder expansion and contraction joints) shall be carefully planned for which there has to be guidelines. 3. Choice of girder shall consider their deflection under load which has influence on Plinth beam and track frame performance. At girder supports rails get additional stress due to differential thermal displacements of Rail and girder and also due to rotation of girders at supports due to deflection under load. Guideline for choice of girders and their configuration will have to be provided for. 4. Type of bearings for girders; fixed or free permitting movement at girder ends has influence on BLT especially where turnouts are located over expansion and construction joints. 5.
Four Rails which can generate as high as 600 kN per rail of thermal force are rigidly fastened to supporting structures. The 200
system can be visualized as one of having fixed/ free end girders supported on piers with rail strings with an axial force of 2400 kN rigidly tied on top of girder irrespective of presence or absence of trains following severe curvatures and gradients (R 120m and gradients 4%). Modeling and assessing the behavior of such a system for forces at critical interfaces like fastenings to beams/ slabs, beams/slabs to girder tops and at bearings are necessary for appropriate choice of configuration mentioned above in 1. 6. Radial component of such high longitudinal thermal force in a sharp curve is to exert a transverse force of P/R per m the effect of which is critical in bearings design. 7. De-stressing temperature is generally fixed on higher side of mean temperature for ballasted tracks to safe guard against buckling. For BLT there exists a case to change this as the critical event will be rail fracture than buckling. 4. Summary: 1. Rigid concrete supporting bases shall be provided only with Ballast-less Track. 2. Indian Railways need to formalize the design parameters outlined above than specifying component specifications like Rail and Fastenings. 3. Structural design of ballast- less track being mostly of empirical and simple, a general design and drawing shall be issued by IR for adoption by IR as well as metros. 4. Organizations adopting ballast-less track shall plan the structure configuration from top down just like construction technique of ballast-less track.
201
Appendix: Design Considerations Typical Plinth Track for Viaduct (i)
The concrete plinths is built on the viaduct deck has to be connected to the viaduct with shear connectors integrally cast in viaduct deck. Typical dimensions for a plinth is as follows. The plinths are generally not more than 5m long with gaps of 100~200 mm to permit drainage and cabling and to limit structural interaction with the viaduct decks. The plinths are reinforced with longitudinal re-bars and transversal frames of which diameters and spacing will be governed by Design requirements.
(ii)
Canted Track: Cant is provided at track level and not at the deck and hence increased height of plinth beams on Cant side is expected.
(iii)
Cross Section: 250mm
TOR min. 414mm
200mm
TOR
630mm
min. 200mm 2.5% The plinths is provided with reinforced concrete derailment guard on the inside or outside of the track for both rails, with the following characteristics:
minimum construction depth (from top of rail to top of viaduct deck) = Top of Rail (ToR) level minus 414mm, 202
varying thickness, on the same cross-section, as per the viaduct deck invert slope of 2.5% and as per the canted track on curve (when applicable),
lateral distance, measured perpendicular to, between the running edge of rail and the derailment guard = 250 +/- 40 mm,
minimum level of the derailment guard upper edge = ToR minus 25mm,
sufficient lateral concrete cover for the outer fastening anchor bolt (at least equal to the anchored length),
clearance of the rail fastenings to permit proper support, installation, replacement and maintenance,
wheels of a derailed vehicle under crush load, moving at maximum speed are retained on the viaduct,
damage to track and supporting structure is minimum.
(iv)
Shear Connectors: the following typical shear connector arrangement is provided for connecting the track plinth to the viaduct deck slab.
Nominal Shear Connectors arrangement 203
Shear connectors positions shall meet the following requirements:
Center line should match with center line of the plinth beam (total width),
Normal positioning is shown in sketch; however a minimum anchorage in the viaduct deck of 160mm is required.
Upper level of the shear connector should be at the same level for all the plinths of the same cross-section,
Provided such that lateral concrete cover is enough to take into account tolerances of construction.
Loads and Combinations: The loads to be taken into account in the track calculation are presented in the following sections. Some of them apply vertically to the structure, other horizontally. The lurching force and the radial force due to thermal expansion are also to be considered. Application
Type of load
Symbol
Dead load
DL
Self-weight
X
LL DY CF RF
Train weight Dynamic impact Centrifugal force Racking force Longitudinal traction / braking force Wind on live load Lurching force Long welded rail load Earthquake Derailment load Radial force due to thermal expansion
X X X
Live load
Other loads
LF WL LF LR EQ DR RT
Description
204
Horizontal
X X
Vertical
X X X X X X
X X
Vertical Loads: Dead Load (DL): This is the self-weight of the track structure, mainly reinforced concrete (given by its weight): DL= 24 kN/m3. Super Imposed Dead Load (SIDL): This consists of the weight of all materials forming loads on the structure that are not part of the structural elements. •
Rail UIC60 : 60kg per meter of rail,
•
Fastening systems: 2 seat of 20kg each (see section 3.3 above) per meter of rail.
Hence: SIDL = 2x(0.6+0.4) = 2kN/m/track. Train Live Load (LL): According to the axle load value at the maximum capacity, the train live load is: LL = 170kN.
Impact Load (DY): The dynamic factor can be calculated by Eisenmann formula:
205
Where: t: multiplication factor of standard deviation = 2; φ: factor depending of track quality = 0.2 (good quality) ; V: train speed = 80 km/h. Hence, the impact load is: DY = Ydyn.LL = 0.46 * 170 = 78.2 kN. Lurching Force (LF): Lurching forces are caused by the train rotating slightly about its axis. As per BS 5400-Part 2 , clause No, 8.2.7, 56% and 44% of the train load is applied. This causes a moment at rail level corresponding to 6% of the maximum axle load multiplied by the distance between rails. Hence, vertical force variation is : Fy = +/- 6 % * 170 = +/- 10.2 kN. Horizontal Loads Centrifugal Force (CF) The centrifugal forces should be taken to act outwards in a horizontal direction at a height ‘h’ of 1.83 m above the running surface of a canted track. The centrifugal force is calculated as per Bridge Rules clause No. 2.5.3(b) : Horizontal load due to centrifugal force: C=
Where : C: Horizontal effect in kN/m run (t/m run) of span, 206
W: Equivalent Distributed live load in kN/m run (t/m run), V: Maximum speed in km per hour, R: Radius of the curve in m. The centrifugal force is assumed to be applied on one rail on curve alignment of radius 120m with maximum speed of 45 Km/h (as per Schedule of Dimensions). This combination produces maximum effect of centrifugal force for which horizontal component is : 2
2
LL*V CFx =
170 * 45 =
127*R
=
22.60kN.
127 * 120
Wind on live load (WL): As per IS 875 (Part-3), clause No. 5.4, the design wind pressure is: pd=KdxKaxKcx0.6xVz². Where: Kd: wind directionality factor = 1, for cyclone affected region. Ka: Area averaging factor = 0.85, linear interpolation of Ka for a tributary rolling stock area of 63.94m2 [(4.048-1.095)*21.65] 2 2 between 25m et 100m (with 4.048m = train height; 1.095m = parapet height ; 21.65m = train length). Kc: combination factor = 1. Vz: Wind Speed for Chennai Region as per cl.5.2 of IS 875 Part-3 = 50 m/sec. Therefore, pd=1275 N/mm2 = 1.275kN/m2. Hence: WL= pdx (4.048-1.095)*21.65/4=20.4kN/axle. 207
The wind forces should be taken to act outwards in a horizontal direction at a height of 1.8 m above the running surface (train center of gravity).
Racking force (RF): The nosing force (racking force) shall be taken as a force acting horizontally, at the top of the rails, perpendicular to the center-line of track. It shall be applied on both straight track and curved track. The nosing force shall always be combined with a vertical traffic load. As per Bridge Rules [clause No. 2.9.1, the racking force value to be taken into account is: RF = 5.88kN/m. Traction & braking (LF): Longitudinal loads from braking and traction are taken as 18% of vertical live load per track. Hence, LF = 0.18 x LL = 0.18 x 170 = 30.6kN (acting on one track). Derailment (DR): For derailment check, we intend to use ACI 358.1R92, clause No. 3.5.2 which corresponds to the application of 50% of one vehicle weight (live load) applied horizontally as a 5m long uniform impact load on member used as derailment wall. Hence, per 5 meter length: DR = 170*4*0.5 = 340kN.
208
Earthquake (EQ) As per Bridge Rules, horizontal seismic acceleration can be calculated by: Feq=W mxah. With: Feq: seismic force. W m: weigth of mass under consideration. ah: design horizontal coefficient = βx/xa0. Where: β: a coefficient depending upon the soil foundation system (worst case β=1.5, clause No. 2.12.4.3). I:a coefficient depending upon the importance of the structure (I=1.5, clause No. 2.12.4.4). a0 : basic horizontal seismic coefficient (CHENNAI :zone 2,a0 =0.02, clause No. 2.12.3.3). Hence: Feq=W mx0.045. Therefore, seismic force in transverse direction per wheel is: EQ = 0.045*170/2 = 3.83kN/wheel. Temperature effect: The temperature ranges (difference between construction temperature and maximum/minimum coming temperature) to be considered on the structures shall be: an overall differential temperature of ±40°C for elevated structures.
209
•
Long welded rail forces (LR)
The maximum longitudinal force induced on plinth by the LWR force is limited to the longitudinal restraint capacity of the fastening system which is: LR = 13kN/fastening. •
Radial force due to thermal expansion (RT)
A curved rail submitted to temperature change will induce a radial force on the plinth, which depends on the rail curvature. Stress in rail RT = Arail Erail α ∆T / R Radial force from
Radial Force RT = 6.45 kN/m.
Stress in
rail Loads summary Type of load Dead load
Symbol
DL Self-weight of track concrete SIDL Self-weight of track material LL
Live Load
Description
Live load
24 kN/m3 2 kN/m/track 170 kN /axle
DY Dynamic impact load CF
Value
78.21 kN/axle
Centrifugal force
22.6 kN/axle acting at 1.83m above
(worst case for Speed & Radius)
the running surface.
210
RF Racking force Live load
LF WL
5.88 kN/m of track
Longitudinal traction/braking force
0.18.LL = 30.6 kN/axle
Wind on live load
20.4kN/axle acting at 1.8m height
(max. speed : 50m/s)
above the running surface
LF2 Lurching force
+/- 0.06.LL = +/- 10.2 kN/axle
LWR load LR
(part of the rail steel expansion from 13 kN/fastening rail to fastener to plinth)
Other
EQ Earthquake
3.83kN/wheel
Derailment load
loads
DR (50% of one coach mass over 5m
340 kN/5m of track
longitudinally) RT
Radial force due to thermal expansion
6.45 kN/m of track in radius
Load combinations The following load combinations (LC1 to LC3) are proposed for track structures based on realistic configurations for a track structure design on viaduct, since there are no codes/standards applicable to track plinth design. The factors are inspired from IRS Concrete Bridge Code and similar projects.
211
LC1: loads combination for normal condition / LC2: derailment / LC3: earthquake
Loads
Dead load Superimposed dead load Temperature effect (LR, radial force) Earthquake Live load Derailment load Wind load
Limit state ULS SLS ULS SLS ULS SLS ULS SLS ULS SLS ULS SLS ULS SLS
Load factors LC1
LC2
LC3
1.4 1 2 1.2 1.5 1
1.4 1 2 1.2 1.5 1
1.4 1 2 1.2 1.5 1 1.6 1 1.75 1
1.75 1 1.75 1 1.25 1
Notes: Wind and earthquake loads shall not be assumed to be acting simultaneously (as per IRS concrete bridge. Live load shall also include dynamic effect, forces due to curvature exerted on track, longitudinal forces, braking forces (IRS concrete bridge).
212
BALLASTLESS TRACK AN OVERVIEW AND DEVELOPMENTS IN INDIA - Vipul Kumar, Executive Director/Track, RDSO, Lucknow - Ashwani Kumar, Director/Track, RDSO, Lucknow - Rituraj, Deputy Director/Track, RDSO, Lucknow
Synopsis: Conventional track, using ballast, has been the norm for a long time. Ballastless track, with the merits of good ride comfort, high stability, high maintainability and little intermediate intervention has emerged important rail structure. This form of track is almost inevitable for suburban and underground sections. The ballastless track also known as slab track is different in structure in different countries. In general, the design theory of ballastless track in different countries is related to its own construction environment, operating conditions, demography and economics. Therefore, the design concepts of different countries as the factors considered in design and the calculation methods vary greatly with each other. For new corridors for high speed and freight traffic, factors such as extended service life, low maintenance, availability and capacity for increased speeds and axle loads will play major role in deciding forms of ballastless track. This paper has been summarized for fastening systems on ballastless track being used on Indian Railways. This paper reviews the performance criterion, technical standards of ballastless track, design methods, parameters as well as the procedures for choosing a particular design of fastening systems for ballastless track in India.
213
Ballastless track structure has many considerations for specific operation type, therefore, along with other important aspects; the design theory of fastening systems on ballastless track needs further study on Indian Railways. 1. Introduction Conventional ballasted railway tracks require periodical tamping due to uneven settlements of the ballast during operation. The sleeper panel must be adjusted to guarantee a smooth run of the wheel sets. Based on the existing experiences this kind of maintenance work is significantly increased for high-speed lines. Ballastless track constructions offer therefore an alternative solution due to the enormous reduction of maintenance work and the long service life with constant serviceability conditions. Furthermore, the application of higher cant and cant deficiency allow the reduction of the minimum values like radii for curves or the increase of speed for lines equipped with ballastless tracks. Unfortunately the initial investment costs for ballastless track superstructures are significantly higher compared with the conventional ballasted superstructures. Main characteristic of ballastless track superstructures is the multilayered design of the bearing structure. The great advantages of ballasted track structures can be enumerated as follows: • Reduction of structure height; • Lower maintenance requirements and hence higher availability; • Increased service life; • High lateral track resistance which allows future speed increases in combination with advance coaches e.g. with tilting feature; • No problems with churning of ballast particles at high-speed.
214
2. Advantages and drawbacks of ballastless track Advantages: • Low construction height and in some cases low track-weight.
• The desired track-elasticity can be obtained more accurately over the whole track length. • The accurate alignment of the track will remain steady throughout its life time. • Less track maintenance means increased track availability.
• Good vibration dampening due to designed resilience levels. • Good electrical insulation.
• Less and very-constant railhead wear.
• Lower stress in rails due to better geometry. • No chemical weed-killing.
• Better access facilities on the track in an emergency for pedestrians and rescue/maintenance vehicles alike. • No lateral distortion or bucking of track. Drawbacks:
• Less flexibility for future layout modifications.
• Generally higher investment costs, unless the ballastless track is installed in a tunnel, on a bridge deck etc.
• Changing the existing ballastless-track alignment is not easy, but the task is not impossible. • To ensure that ballastless-track noise levels are no higher than that of ballasted track, noise-reducing measures must be taken; otherwise ballastless track will produce more noise than conventional track.
• Ballastless-track construction must be carried out very accurately because correction is expensive and timeconsuming. 215
• Damage repair after derailment takes more time and is more complex.
• Conversion from ballasted track to ballastless track is timeconsuming, which means that the ballastless solution is less suitable for track replacement but more relevant for building new lines. • Improper design of resilience may lead to higher noise and vibration and the corrective measures may be complex and expensive. 3. Classification of Ballastless track The ballastless track is classified in many ways e.g. based on resilience system - single, double; based on cost; etc. To begin with, the following classification looks more relevant from Indian Railway perspective based on type of support construction used i.e. a) Ballastless track on earthwork b) Ballastless track on bridges c) Ballastless track in tunnels
Ballastless track on embankment 216
Ballastless track in tunnel/
Ballastless tracks are best suited for locations where there is no or little possibility of settlement. Viaducts and tunnels are therefore the ideal & best suited locations for ballastless track. However, on earth formations, the sub grade structure is required to be properly designed for ballastless track so that minimal settlement of track during service is ensured to avoid need of any intermediate maintenance. A second classification has been introduced in respect of fastening systems used for the slab-track system as follows: i) Compact systems: slab track with concrete sleepers placed in situ concrete, like Rheda, Zublin, etc. ii) Baseplated systems: concrete slab-track with elastically supported base plates on the top of the slab. iii) Coated concrete-sleeper or concrete-block systems: These sleepers or blocks are fixed in a concrete support construction by a resilient intermediary material. This material with resilient properties can be a rubber boot or an embedding material. 217
iv) Embedded rail systems: slab track with continuouslysupported embedded rails in a concrete slab (with recesses) or in steel channels on bridges. v) Prefabricated slab systems concrete prefabricated slabs, either reinforced and/or pre-stressed with any rail fastening design. The slabs can be connected to the concrete supporting structure using mortar. In this case the slabs can be rather thin. Thicker slabs can be supported on a stabilized-sand layer, a grout and even on a combination of both. If the low-maintenance characteristics of slab track on open line are to be retained, great care must be taken to ensure that the sub grade layers are homogenous and capable of bearing the loads imposed. The slabs may be prefabricated or poured on site. The high level of investment required has prevented widespread use of slab track on open line so far. The most well known slab track structures, presently in use, are: • Rheda, Züblin and other variants (Germany); named after the places where these types were first used, in both these systems, sleepers are cast into the concrete slab, generally with second pour.
Rheda 2000 track system
218
• Stedef, Sonneville Low Vibration (France); Most often used in tunnels. This technique is also used for high speed. The rubber boot under the sleeper/ block provides high degree of elasticity which in turns ensures good noise & vibration insulation.
Stedef twin block track system
• Walo (Switzerland); This system is mainly used in tunnels. In this system, first a special slip form paver lays a concrete track base and installs a cable duct. Then the twin block sleepers fitted with rubber boots are placed in position and cast into place.
219
• Edilon block track (Netherlands); mainly used for bridges and tunnels. This system is installed “top down”. First the rail & blocks are placed in position. Then the bocks are cast in Corkelast in order to provide necessary elastic support. This is among the earliest forms of ballastless track form developed by NS.
• Shinkansen slab track(Japan, South Korea); This system consists of a sub-layer stabilized by means of cement, cylindrical stoppers to prevent lateral and longitudinal movement, reinforced prestressed concrete slabs and bituminous cement mortar injected under and between the slabs. The slabs weigh about 5t each. This is among the most expensive ballastless track forms.
220
• IPA slab track (Italy); this system is based on the systems used in Japan. • ÖBB-Porr (Austria); Mainly used in tunnels and viaducts. This system comprising embedded monoblock sleeper enclosed in rubber is very similar to German zublin design. There is also a variant – Porr system which uses prefabricated slabs.
• Embedded Rail Structure (Netherlands). This system provides continuous rail support by means of a compound consisting of Corkelast, a cork/polyurethane mixture developed by Edilon B. V.
Embedded rail track system 221
4. Design considerations of ballastless track structure Ballastless track has been defined as track where the ballast is replaced with a concrete slab, asphalt slab or steel base with the use of additional pad generally in lieu of ballast resistance. Concrete slabs can be either continuously poured on site or made up of prefabricated slabs. Asphalt slabs are usually made of continuous compacted asphalt material. Steel bases or girders are also used on bridges. In some cases not only the ballast but also the sleepers have been replaced with slabs. This definition clearly shows that it is rather easy to effect a separation between the slab itself and the rail fastening system used on the slab. Rail fastening systems which can be used on slabs for ballastless track are nearly always suitable for application on steel and concrete bridges and in tunnels. The bearing structures of the ballastless track mainly include: a)
Plain concrete
b)
Reinforced concrete and
c)
Prestressed reinforced concrete.
The plain concrete structure is usually applied to the tunnels with good foundation and small ambient temperature variation. In this case, the slab will not crack under the action of train load and environmental factors. Under the common foundation conditions, the slab may readily crack with the influences of foundation deformation, train load, and environmental factors. Thus, it is necessary to add reinforcements to limit the crack development. The reinforcement concrete slab, because the temperature stress is the main influencing factor, reinforcements are laid near the neutral axis to limit the crack width and crack interval of the track slab. For the sections with severely weak foundations, the bending moment in the slab is usually large. In order to limit the crack width, we need to thicken the slab or improve the foundation, which results in high costs. In that case, placing reinforcements in top and bottom 222
layers can help the track slab bear more bending moment. To limit the crack width and improve the structure durability, steel fiber concrete has been increasingly used in the ballastless track structure. The prestressed reinforced concrete structure is often adopted in cold areas for decreasing the freezing injury. The allowable stress method and the ultimate state method are generally utilized in the concrete structure design. Considering factors such as construction and costs, the prestressed reinforced concrete structure designed by partial limit state theory is applied.
5. Design of fastening system for Ballastless track Owing to initial development of slab track in Netherland and Europe the vast experience is available with these railway systems. Accordingly, first specifications have also been drawn there with lots of work and studies still continuing. EN 13481-5 shall be used for fastening system. Following important aspects should be considered in design; a) Vertical stiffness of fastening system: As per EN 13146-4 b) Attenuation of vibrations: As per EN 13481-6 c) Longitudinal restraint: As per EN 13146-1 d) Life of fastenings system: As per EN 13146-6 e) Permit electrical insulation: As per EN 13146-5 f) Adjustment to permit regulation of rail position (vertically or laterally) g) Permit the attainment of the permissible tolerance when installed and later during service
223
6. Experience of IR on Ballastless track There has been very little experience of ballastless track on Indian Railway in the form of washing aprons. Earlier, RDSO had developed few designs of washable apron based on interaction/ discussion with zonal railways which were issued to Zonal Railways for trial and submitting feedback to RDSO. During interaction with some zonal railways, it was understood that these designs are not proving adequate in long run and giving frequent trouble. Few railways have developed their own designs for washable apron. One such design developed on Central Railway and laid in 2005 is available on P.C. No. 5, Mumbai end Pune station. However, no feedback data is available for these designs. Some zonal railways have used RHEDA 2000 system, a patented design for washing aprons which is a monolithic ballastless track system design of German origin. The system has bi-block sleepers connected by steel lattice embedded in reinforced concrete slab. Actual experience of ballastless tracks in India has come from Delhi Metro Rail Corporation since 2002. The system used in DMRC is fastening system 336 on viaduct/tunnels. Further, in few tunnels of USBRL and on DAMEL project, RHEDA 2000 &300-1-U Fastening system has been used. Now, many other metros will also be coming up with other or similar fastening systems on their ballastless track. As per Metro Railway (Amendment) Act 2009, Ministry of Railway has been entrusted with technical planning and safety of Metro Railways. For selection & approval of fastening system for metro railways, Railway Board vide letter No. 2009/Proj/MAS/9/2 dated 21.05.2010 have issued “the performance criteria of fastening system for Ballastless track for Metro Railways / MRTS Systems” and metro railway are required to use fastening system fully compliant to this performance criteria. Further, as per Railway Board’s letter No. 2009/Proj/MAS/9/2 dated 19.08.2010, for using non-compliant fastening systems, prior approval of Ministry of Railways is required. 224
7. Performance criteria of fastening system for Ballastless track The performance criteria of fastening system for Ballastless track for Metro Railways / MRTS Systems has been issued by Railway Board vide letter No. 2009/Proj/MAS/9/2 dated 21.05.2010. The important features are as under; 7.1 Purpose: The performance criteria define the performance standard of fastening system for ballastless track of Metro Railway System. Apart from other things, the fastening system is required to moderate vibration and noise transmitted through the rail and to reduce the track stiffness and the impact on the track structure, so as to obtain the parameters as detailed in the ensuing paragraphs. 7.2 Operating Environment: Fastening system is expected to perform generally in the following conditions: i)
Gauge - Broad Gauge, 1676mm (nominal), standard gauge1435mm.
ii)
Speed potential - 110kmph
iii) Rail section - 60 kg, UIC, 90 UTS, 110 UTS iv) Guard rail - Inner guard rail on viaduct and double/multiple line tunnels v)
Static axle load - BG & SG - 20t (max.)
vi) Design temperature range: -10 degree Celsius to + 70 degree Celsius (rail) In addition, the client Railway may specify the other operating condition such as minimum radius of curve, super elevations, cant, ruling gradient & support spacing. 225
7.3 Ballastless Track Structure: Track shall be laid on cast in situ/precast reinforced plinth or slab, herein after referred to as the ‘track slab’. The track slab shall be designed as plinth beam or slab type ballast less track structure with derailment guards. It shall accommodate the base plates of the fastening system. The minimum depth of concrete below the base plate should be decided based upon characteristics of underlying base and the design of the fastening system. In general, track slab on which the fastening and rail are to be fitted shall: i)
Resist the track forces.
ii)
Provide a level base for uniform transmission of rail forces.
iii) Have geometrical accuracy and enable installation of track to the tolerances laid down. iv) Ensure drainage. v)
Resist weathering.
vi) Be construction friendly, maintainable and quickly repairable in the event of a derailment. The ‘Repair and Maintenance methods’ shall be detailed in a Manual to be prepared and made available. vii) Ensure
provision
consecutive
for
electrical
continuity
between
plinths/slabs by an appropriate design.
7.3.1 Derailment Guards The lateral distance measured perpendicular to between the running rail and the guard rail shall be 250 to 300 mm. It shall not be lower than 50 mm below the top of the running rail and should be clear of the rail fastenings to permit installation, replacement and maintenance. Derailment guard shall be designed such that in case of derailment: 226
i) The wheels of a derailed vehicle under crush load, moving at maximum speed are retained on the viaduct or tunnel. ii) Damage to track and supporting structures is minimum. 7.4 Performance Requirement of Fastening System: 7.4.1 General i) The fastening shall be designed to hold the two rails of the track strongly to the supporting structure in upright position by resisting the vertical, lateral and longitudinal forces and vibrations. ii) The fastenings shall be with a proven track record. Fastening System should have performance record of minimum five years in service in ballastless track on any established railway system. In this regard, supplier should submit certificate of performance from user railways administration including proof of use of the fastening system. iii) The fastening shall provide insulation to take care of return current of traction system. iv) Fastening should satisfy the required performance norms as stated in para 7.4.2, 7.4.3, 7.4.4 & 7.4.5. 7.4.2 Following are the technical performance requirements of fastenings: The Fastening shall: i) Have design service life of 30 years in general. However, its c0. ii) Components such as rubber pad, rail clip etc. can be designed for 300 GMT or 15 years whichever is less. Anchor bolts or studs used for fixing base plate to the concrete should not be required to be replaced during service life. Its components must 227
not suffer any degradation during its service life to a degree so as to affect the performance and safety of the track. Full service life is to be attained under the following conditions: a) Atmospheric ultra violet radiation. b) Proximity of track up to 10 m from salt water source. c) Contact with oil, grease or distillate dropped from track vehicles. ii) Hold the rails to gauge and at the correct inclination within, tolerances laid down, against horizontal forces generated by vehicles in motion especially on curves, wheel set hunting, alignment irregularities and thermal forces. iii) Permit quick and easy installation and replacement with special tools. iv) Be capable of vertical adjustment during service life upto 12mm using shims. v) Permit the attainment of the following tolerances when installed, and later, during service. S. No. 1 2 3 4 5 6
Parameter Gauge Cross level on straight track Super elevation on curved track Vertical alignment over a 20m chord Lateral alignment over a 20 m chord on straight track On curves - variation over the theoretical versine on 20m chord 228
Installation
Maintenance
+2, -1 mm +1.5 mm
+4, -2 mm +5mm
+1.5mm +3 mm
+3mm +6mm
+2mm
+6mm
+2mm
+5mm
8. Technical specifications of Ballastless track Railway Board has also approved and issued “Technical standard/specification for track structure for Metro Railways / MRTS Systems” developed by RDSO covering details of curvature, gradients, turnouts, switch expansion joints etc. for use on metro system in the country vide their letter no. 2010/Proj./Genl/3/3 dated 23.12.2011, which states that fastening system shall conform to the requirements of performance criteria as elaborated in Para 7 above. 9. Conclusion Ballastless track with many of its advantages, particularly its long service life, safety of operation and lower lifecycle cost is gaining popularity. Presently, many ballastless track assemblies have appeared in the railway market. For further development of the alternative designs, the experiences borne during the installation and by monitoring during service life on existing MRTS systems on IR/Metros will be very important. Therefore, not only depending on special systems developed and provided by different companies, we should come forward with potential new ideas for optimization of ballastless track systems on IR. To meet the transport needs of fast growing economy in countries like India, there is good scope for adoption of ballastless track technology. However, it is very important to know about the best ballastless track suitable for given environmental & operating conditions as one variant may differ materially from other in terms of cost and durability. It is imperative that the ballastless track structure designed is conceived in compatibility with the rolling stock and civil structure. Piecemeal approach on the subject may be detrimental as number of disappointments has occurred all across the world. It is for this reason that there is lot of work still going on internationally on the subject and Indian Railway can take advantage of the same as well by close interaction with advance railway systems.
10. References a) Application and experience with ballastless track (UIC). b) Innovations in railway track by Coenraad Esveld. 229
SELECTION OF BALLAST LESS TRACK FOR INDIAN RAILWAYS Naresh Lalwani, Sr. Professor/Bridges/IRICEN Pradeep Kumar garg, Sr. professor/Track/IRICEN _______________________________________________________ Synopsis: Ballast less track is in use on the World Railways since last 4-5 decades. Its use is not only limited to tunnels or bridges or station yards but ballast less track is being used on open track meaning on banks and cuttings under the open sky also in some countries. Popular understanding on IR is that ballast less track is provided on locations where carrying out the regular track maintenance is difficult. Station Yards and tunnels are the only two areas where ballast less track has been used on Indian Railways. However on Metro systems, ballast less track is routinely being used even on the elevated sections. The adverse factor for choice of BLT is its high initial cost in comparison to ballasted track. The major advantage of BLT apart from very low maintenance requirement is excellent track geometry parameters; and that is one of the reasons of the low maintenance requirements. For station yards we are forced to use BLT due to functional requirement of cleanliness while difficulty in track maintenance in a tunnel makes it imperative to use BLT there too. There are other areas where BLT can be a far better solution than conventional track. This paper aims at explaining in simple words various types of systems used on the world railways and their experiences. Attempt has been made to identify areas where BLT can be used as a choice rather than a last resort arrangement.
231
1.0 Introduction: 1.1 Ballastless track, as the name implies is track without ballast. Most of the tracks on the railway systems are ballasted wherein ballast provides the needed resilience to the track and permits the correction of track geometry. However, in 1960s some of the railways started laying ballastless or slab track for specific applications. The main advantages of the ballastless track over the ballasted track being the lesser maintenance, higher track availability, longer life, reduced tunnel cross section, lesser dead load on bridge viaducts etc. to list a few. The use of ballastless track on Railway systems in European countries such as Germany, Netherlands, Italy, France etc. and in Asian countries such as Japan, China etc. has been gaining popularity over the years. Ballast provides about 50% of the resilience and a good vibration and noise absorbing functions in a conventional track and once we do away with the ballast, ballastless track has to take over these functions. Necessary elasticity is provided by rubber pads used as resilient layers. 1.2 The cost of any asset is not merely its acquisition cost but also includes the cost of keeping the asset in good shape and its availability for use (hours per day and days per year). All this can be captured in three words “life cycle cost”. Use of BLT has not only to be seen in this context but has advantages which go beyond the life cycle cost concept. Owing to very good track geometry, the life of the rails and rolling stock as well as fuel consumption also exhibit marked improvement apart from increased passenger comfort. These advantages should be the propelling force for making us think of BLT for areas of track other than station yards (what we popularly call washable aprons) and tunnels on Indian Railways. Then there are sections where maintenance is difficult due to extensive usage 232
and very high occupation during the day time like busy Mumbai suburban system. Drainage, soiling of ballast, loss of ballast is another set of issues in some of the sections where manual maintenance is unthinkable, particularly in approaches of major cities. Proper maintenance of track on steel bridges is still a challenge which we are yet to overcome. The standard track structure on steel bridges provides for steel channel sleepers with complicated fitting and fixing arrangements. BLT can be thought of as a solution. This paper aims to discuss the area where BLT can be a desirable alternative. 1.3
Japan was the pioneer in use of Ballastless track and has extensively used BLT on high speed tracks. Germany is another country which developed its own system popularly known as RHEDA. Netherland worked on the embedded rail system. China has gone in a big way for use of BLT for its high speed network. It has adopted base plated system for track with speeds up to 350 Kmph.
2.0
Types of Ballastless track Ballastless slabs can be classified based on different criteria. This is being mentioned to make the readers familiar with these different kinds of classifications and terminology.
2.1
Based on the number of resilient layers the ballastless tracks are classified as single resilient layer BLT and two layered resilient track BLT. The example of single resilient layer system is embedded rail system with pad underneath the rails. In the two layer systems there is one rubber pad under the rail with another one either under the base plate (on which fastening arrangements are provided) or under the sleeper. Compact systems like RHEDA and various designs of base plated systems are examples of the former and Block type system are
233
examples of latter. These are explained below in brief along with sketches.
Figure 1. Single resilient layer and Double resilient layer BLT Systems
2.2
Systems are also classified based on nature of support provided to the rails – punctual or discreet is one kind and continuous support to rails is the other kind. All systems except the embedded rail system are examples of the first.
2.3
Based on type of construction, there are basically five kinds of BLT systems being used in the world. We are not talking of different proprietary systems as there are many but five kinds of different arrangements of BLT. This kind of classification is considered more appropriate to differentiate various systems and therefore is elaborated below. Different Railways have used these systems and each system has some distinct advantages. Though all the systems have been used for axle loads of around 225 KN and speeds above 140 Kmph, we can’t say that any system is inferior or superior. By virtue of their characteristics, some system may be more suitable for a given 234
area of track. This paper aims to give an understanding of these five different systems and their suitability for different applications. These systems are explained in brief below to understand the basic characteristic of each of the track based on which it is proposed to build the discussion on the suitability for different applications. 2.3.1 Compact Systems These systems are pioneered by Germans and are used in many countries. The salient features of this system are
Figure 2. Compact System with TBC with lattice tie connection
235
• Mono block (MBC) or twin block (TBC) concrete sleepers by one of the two methods o Embedding sleepers in concrete by pouring fresh concrete underneath and around the sleepers (RHEDA type design, being used in J&K Project in Udhampur-Katra Section) o Inserting and bonding the sleepers in fresh concrete by vibration (Zublin type design) • Used in earthwork in cuttings, in tunnels and in short bridges <=25m and these are built as continuous RCC layer. • When used in embankments, a hydraulically stabilized layer (HSL) is provided below the concrete layer. Frost protection layer (FPL) is also provided wherever necessary. • Longitudinal reinforcement steel (0.8 to 0.9% of cross section) is provided in RCC layer through the holes (if MBC) or through the tie/lattice of TBC and that too only for axial forces due to temperature. • Use of TBC with two blocks joined by lattice girder (made of steel bars) is preferred over MBC as it has a better bond. • Due to system being monolithic, entire cross section of slab plays a structural role, resulting in optimization of design. • Has been used for axle load of 225KN and speeds up to 250 kmph 2.3.2
Baseplate Systems Netherlands was the first country to use this type of system. The features of the system are:
236
Figure 3. Base Plated System
• Steel baseplates mounted on steel or concrete surface – i.e. concrete bed with holding down bolts with suitable interface arrangements (Kolkata metro used this system) – there are no sleepers in this system. • Resilient and stress distributing pad is installed in between. • Finishing of the surface on which base plates are fixed has to be done very accurately and smoothly as that is the foundation for the base plates.
237
• For durable top surface if concrete (as is the case mostly), the weak top layer of concrete has to be removed by grinding otherwise it may get worn out by water and abrasion. • Wearing of bolts holding the base plate is a serious problem and requires solutions in the form of replaceable bushes etc. • Since vastly different systems have been used since 1955, they are not comparable. • Has been used for axle load of 225KN and speeds up to 350 kmph. 2.3.3 Block Systems These systems use MBC/TBC sleepers like the compact system but the sleepers are either coated with resilient envelope and concrete is poured under and around the coated sleepers. Alternatively, these are fixed in prefabricated troughs in hard concrete with resin poured after alignment of the track to embed the sleepers. This has been used on many countries like Austria, Belgium, Eurotunnel and Switzerland. In India this system has been adopted in long tunnels on Konkan Railway and also in tunnels in Jammu-Udhampur section. The features of this system are 1. Slab 2. Sleeper Block 3. Tie Rod 4. Monoll l
Figure 4. Block (Booted) System 238
• The elastic resilient material is provided between the sleepers and the surrounding concrete by either of three ways o Prefabricated boot made of some elastic material which includes a resilient under sleeper pad o Rigid hull with lateral resilient pads o Pouring elastic material around the blocks/sleepers to embed them • Two layers of resilient pads - one under the rails and other under the sleeper • Has been used for axle load of 225KN and speeds up to 230 kmph 2.3.4
Embedded Rail Systems
As the name suggests, rails are placed in the groove and filled with pourable elastomer material. These have been used in Netherlands on concrete deck bridges and steel bridges. Example of this is EDILON embedded rails. The main points of this system are • No sleepers used • The rails are continuously supported • Embedding material acts as the only fastening for the rails
239
Figure 5. Embedded Rail System
• In addition to the embedding material, there is one more layer of resilient material under the rail • Has been used for axle load of 225KN and speeds up to 140 Kmph on concrete and steel bridges 2.3.5
Prefabricated Slab Systems This system consist of prefabricated RCC/PSC slabs into which the fastenings systems like Vossloh / Pandrol base plates, embedded blocks or embedded rails are incorporated. The salient features of this system are
Figure 6a. Prefabricated system in Japan 240
Figure 6b. Prefabricated system in Japan
•
No sleepers are used and prefabricated slabs can be considered as sleeper blocks
•
Construction by leveling of the slabs to exact alignment with spindles, connecting to the supporting structure by pouring mortar of semi rigid material underneath the prefab slabs.
•
Can also be laid on layer of stabilized sand in combination with inject grout
•
3 subsystems are used o Low mortar thickness – acts like the compact system o
High mortar thickness – slab and the supporting structure act independently with mortar layer behaving like a resilient separation layer
Use of thin concrete slabs in above two situations as the aim is to have a sandwiched construction. Have been used in Austria in tunnels as well as open air and on tunnels in Italy. Experience also available in Germany, Netherland and Japan. Japan Shinkasen system is primarily of this type with additional arrangements for floating track. o
•
241
3.1
Applications of Ballastless Track in India It was Metro Railway in Kolkata, which provided the first opportunity for use of BLT on a considerable scale. Tunnels in Konkan Railway were the second project where BLT was used followed by again in tunnels of Jammu Udhampur sections. Prior to these, it was only on platform lines of busy passenger stations that BLT called by the name ‘washable apron’ was used. Washable apron was a kind of compact system with rudimentary arrangement of under sleeper resilient layer in the form of bitumen material. The performance has not been satisfactory. The major reason which can be said to run across all the applications for dismal performance was indigenous efforts without having the sufficient experience. We should have paid for and imported the technology. Second reason is not doing it the way it has to be done. Any good system will fail if not executed as per the strict technical requirements. It is only in the recent past we have started using the proprietary system of RHEDA for washable aprons. Metro systems on the other hand have gone in a big way for BLT, namely Kolkata Metro, Chennai Metro and Delhi Metro.
The experiences of Indian Railways are explained in brief as below. 3.2
Kolkata Metro The first BLT was laid on Indian Railways on Kolkata metro in 1984. Three types of ballastless track were designed and developed for Kolkata metro. These were called M-1 (later changed to M1-A), M-6 and M-7. These assemblies were tested in RDSO/Lucknow as well as under running trains on trial tracks laid at Majerhat with assemblies of these types. Out of these three designs, only M1-A design was used on most of the locations due to its better performance. This is a base plated system and the salient feature are. 242
Figure 7. Base Plated system in Kolkata Metro
•
Rails are fastened to cast iron bearing plates by pandrol clips.
•
There is a 6 mm thick grooved rubber pad between the rail and the cast iron bearing plate.
•
Second layer of resilient pad consists of a 12 mm thick specially designed grooved rubber pad below the bearing plate.
•
Below this, packing steel sheets of appropriate thickness may be inserted to obtain levels accurately.
•
The C.I. bearing plate and the 12 mm thick grooved rubber pad together with steel packing sheet, if any, are fastened to the concrete bed through specially designed anchor studs. These anchor studs are made of alloy steel.
•
The anchor studs are fixed into high-density polythelene inserts, which are fixed in the holes provided in second pour concrete. For fixing these inserts, epoxy resin mortar of suitable composition is poured in the holes. Nylon ferrule around the anchor studs is provided to insulate the same from the bearing plate. Electrical insulation is achieved by the use of grooved rubber pads and nylon ferrules.
•
Specially designed triple coil spring and washers were used at the top ends of the anchor studs, to ensure that the fastening units do not become loose in service. 243
•
No adjustment of gauge or alignment is possible in such a type of assembly. The levels may be, slightly adjusted by inserting steel packing sheets below the 12 mm thick grooved rubber pads.
•
The top surface of the second pour concrete bed is longitudinally and transversely sloped in such a manner that any water falling on it can be drained out to a central drain provided along the length of the track. These drains ultimately discharge the water in sumps placed at different locations. The major problems faced in the maintenance of M1-A BLT are as below:
•
The concrete bed got separated from the tunnel base leading to longitudinal cracks and water percolation in the gap.
•
Due to bottom up approach of construction, track geometry achieved was lacking the requisite tolerances desired for BLT.
•
The construction methodology was later modified to Top Down Approach so as to achieve better track geometry.
Figure 8. Top down approach of construction in Kolkata Metro 244
3.3
Konkan Railway: BLT was provided in 6 longest tunnels on Konkan Railway in 1994 totaling to about 22 Kms, the salient features of which are as below.
Figure 9. Block system with MBC sleeper in Konkan Railway
• The design adopted was block system wherein the resilient pads were provided at the bottom as well as on the sides of mono block pre-stressed concrete sleepers. • Construction approach was bottom up type. A firm concrete base with pockets (grooved) was provided for sleepers which are laid on rubber pads, surrounded by foamy substance and voids filled with special expansive (non-shrink) grout. • Main problems being faced are the working out of the resilient pads and loosening of the sleepers due to vibrations and ingress of water seeping in the tunnels. This resulted in deterioration of track geometry. The repairs being done through grouting etc is costly and not a permanent remedy. 245
3.3
Chennai MRTS: In Chennai MRTS, base plated system on plinth beam has been used. The construction technique is improvised top down approach so as to get good quality control on track parameters. The fastenings are Voslloh fastenings to hold the rails onto the base plates. The raised concrete on the plinth beam performs the function of the guard rail. A completed segment is shown in Figure 10.
Figure 10. Base plated system used in Chennai Metro
The BLT has recently been used on other metro systems also like on Delhi Metro. On Jammu-Udhampur section also, BLT has on the pattern of the Konkan Railway design has been provided in one of the tunnels in operation. It is learnt that that the problems have been reported in few stretches in this tunnel also. If we talk of the ballastless track in station yards on our system, these are mainly the platform lines washable aprons with different designs. None of the old designs adopted are able to perform satisfactorily in spite of various innovations made from time to time. Recently, Rheda system has been provided at few places and reported to give satisfactory progress so far. 246
The problems faced on Indian Railways are in no way reflection on the success or failure of the particular system of ballastless track. They reflect more on the way the systems have been designed, modified and executed. It needs no emphasis that key to having a good quality BLT is strict adherence to the execution methodology and quality control. Everything hinges on the strict geometric tolerances and high degree of stability of the sub-grade on which the BLT system rests. Kolkata metro’s base plated system has not been successful but the same systems are used for high speed lines of China. Even the Airport line of DMRC on which RHEDA has been used is facing issues and line had to be closed after opening. Though a committee is appointed to look after the issues but doubts are being expressed about the changes is design to the BLT system. Since we do not have much of experience of BLT on Indian Railways, we should not shy away from using the technology from the original firms who have developed the system rather than adopting indigenous systems created by modifying the original systems without doing adequate R&D and real experience. 4.0
Areas of application of BLT on Indian Railways As stated in the beginning, the use of BLT has been in areas where it was inescapable like unmanageable platform lines on busy stations, tunnels, metro/MRTS systems as a measure of last resort. But there are other problem areas, where BLT can be not only a viable but desirable alternative from practical considerations. Probable areas and the reasons for use of BLT in those are discussed in brief along with recommended type of BLT system with logical reasons for recommendation.
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a) b) c) d) e) f) g)
Platform Lines at busy stations Tunnels Metro system (elevated) Steel and concrete bridges Deep cuttings with erodible slopes and approaches of major towns Suburban sections Areas where ballast quarries are banned
Before talking about the individual track areas it is reiterated that each of the systems is by design suitable to be used in all the applications. However, each of the systems has typical advantages which make it more suitable for a certain application out of the ones listed above. From practical considerations there is no point in having all the types of BLT systems. We should stick to 2-3 kinds of system out of the 5 listed in 2.3 above. Block system (booted system) is a good system and quite extensively used all over the worlds and is suitable for high speeds too but it has been not without maintenance problems in KRCL. The reason for its failure is the way it has been designed and executed. MBC sleepers have been used and they have been laid in grooves in concrete with rubber pads under the sleeper and on the sides with resin filled in the spaces around the sleepers. Quality of rubber pads on IR is a sore point. If the rubber pad stops providing the resilience than it would not take much time leading to separation and loosening of sleeper from the surrounding concrete. This would then accelerate the deterioration of the system with easy ingress of water and fines. That is what happened on Konkan Railway. It is maintenance Engineer’s nightmare and so also of an environmentalist due to high decibel noise. In the hindsight going in for a proprietary product with rubber pads manufactured by the system installer appears to be right approach. 248
Prefabricated system is although appears to be a good system but it would require very high level of accuracy in preparation of drawings and achieving casting of prefabricated sleepers suiting to track alignment in curves etc. This system has been extensively used on the high speed line in Japan and is a proven technology. As compared to this in other three systems the accuracy is achieved by aligning and leveling the actual rail, and site casting of concrete, which is more intuitive to IR engineers. Moreover this is the costliest of all the systems. So use of this system on IR at this stage is not recommended. Experience in base plate systems on IR has also not been encouraging due to following reasons •
Base plate does not act as an integral part of the BLT system due to bolts used for fixing the base plate generally fixed in the ferrule. Higher level of vibrations tends to get generated due to play in the fittings. This has been overcome by having embedded bolts/inserts.
•
Loosening of the bolts resulting in maintenance problems including cracking of the concrete underneath.
•
Bottom up approach of construction practiced in the earlier BLTs.
But most of these issues have not plagued BLT in Delhi Metro’s improvised design, where base plated system has been used extensively. Let’s discuss about the individual BLT locations and preferable system for it. a) Platform Lines at busy stations – Platform lines suffer the worst abuse from pollutants like muck, night soil, urine, rubbish and water. These pollutants do remain on the track for longer durations. Compact system would be the most suitable 249
for this as this is the most impermeable solution. Embedded system can also be thought of but the life of the resin under such trying conditions would be less. If that problem can be sorted out, embedded system can also be an acceptable solution. IR is presently using Rheda, which is a compact system. In addition to going for BLT for the length of platform, we can think of having BLT for turnouts too at least in new yards in metros or busy passenger stations. b) Tunnels – One of the advantages of using BLT over ballasted track in the tunnels is reduced cross section of the tunnel, apart from the maintainability considerations. Another safety requirement in the tunnels, particularly long tunnels is the accessibility for rescue operations in emergency by rubberized tyred vehicles. In long tunnels, another constraint is difficulty is carrying out maintenance operations, due to poor ventilation (even when forced ventilation is provided), as staff cannot work for long durations. All these requirements can be best achieved by using embedded rail systems, where the top surface is even like an ungraded crossing. Other advantage of the embedded system is absence of fittings, which suits as regular maintenance of fittings in tunnels is comparatively difficult. Cost wise also it would be comparable with other systems. Though embedded rail system is with single resilient layer but continuous encasing of rails provides additional resilience. So given the choice and other factors being comparable, embedded system would be the recommended system for tunnels. IR does not have any experience of this. c) Metro System (elevated) – In the of Delhi Metro base plated systems with Vossloh have been used but these are for lower speeds up to 80 Kmph and therefore for Airport line of DMRC RHEDA system has been used. Chennai metro uses the base 250
plate system with Voslloh fastenings. RHEDA system is considered suitable as also embedded system. d) Concrete and Steel Bridges – Track on steel bridges is mostly on steel channel sleeper. Channel sleepers are costly, its maintenance is difficult and it is heavy. Due to its weight, it is almost impossible to do the painting of sleeper seat area. Accumulated neglect due to this would cause corrosion of sleeper seat and this is likely to become a serious issue in time to come. Tightening of fittings is another issue. Netherlands has gone in a big way for use of embedded BLT system for steel bridges even for longer span. We can think of the same for IR for plate as well as Open web girders. We can even think of this for mega steel bridges like Bogibheel, where the work of superstructure has just started. Except for the weight, use of embedded systems would solve all the other problems associated with channel sleeper track. Though in small bridges, the hassles for providing transition track between the BLT and ballasted may be a costly and complicated affair, we can think it feasible only for major bridges by fixing a minimum length of bridges. Though we are no longer going for concrete bridges (PSC) for spans above 24.4 m as per extant instructions, still we can think of BLT as a solution. In the ballasted deck of these bridges, deep screening by machines is not possible due to less width of deck. e) Deep Cuttings with erodible slopes and approaches of major towns – The problem in both these locations is non-feasibility of carrying out regular track maintenance due to regular contamination of ballast. Trains have to be slowed down in these stretches. BLT could be thought of as permanent solution. The intent is not to include boulder falling cuttings, where there is likelihood of permanent damage to BLT. 251
f) Busy Suburban Sections – Maintenance in suburban sections is difficult. Platform lines form a substantial portion of track, where packing by machines is difficult and deep screening by BCM is not feasible. No window is available in day time for carrying out maintenance operations. For these reasons the staffing levels are higher as compared to normal lines carrying the same traffic. Fouling of ballast is also more and removal of deep screened muck is prohibitive. Cost of construction is very high in suburban sections due to many reasons including rehabilitation costs. So provision of BLT in lieu of conventional track will not substantially affect the estimates. In new suburban lines, this should be made the standard track structure. Track on existing suburban lines can also be converted to BLT by using patches of new suburban lines if situation permits. g) Areas where ballast quarries are banned – In the state of Punjab, Haryana and Uttaranchal, quarrying of ballast has been banned. Ballast is being transported from nearby states in railway wagons. This will be a costly proposition as on the saturated railway lines, it would eat into the traffic paths in addition to cost of haulage. It would also not be a greener option. We may have to think of BLT at least on new lines in these states. 5.0
Conclusions
Increased use of BLT on IR is the need of the day and in areas more than what has been hitherto done. Efficacy of BLT systems is proven worldwide. Concept of life cycle cost has to be inculcated in the minds of not only engineers but finance wings too. We need more BLT on IR.
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We suggest use of three systems namely compact; base plated and embedded systems as deliberated above. In the initial phase, the tendering should keep provision of license/technical intervention by the original firms. We should not be shy of paying for the right technology like we do in procurement of track machines. After having developed the experience and the confidence, we can go for technology transfer of the system selected. Works of such precise nature cannot be done by any civil contractor as is also the practice world over. Once we allow unprofessional firms to enter, it forms a vicious circle. Technical competence cannot be developed overnight and it takes time and expenditure to develop not only competent supervisors but right skilled workforce. Until the firms are sure of getting regular business, they would not invest in this endeavor. So restricting such high precision works to small number of the competent firms may appear to be a costly proposition in short run but will result in construction of longer life track structures. If the works are not done professionally, we will be blaming the proven technology as normally happens, and in the bargain we as an organization will be stuck with the low technology solutions. References: 1. “Ballastless track – Application and Experience with Ballastless Track” by UIC 2. “Low-Maintenace Ballastless track Structures” by Coenraad Esveld 3. “Innovations in railway Track” by Coenraad Esveld 4. “A Treaties on Konkan Railway” published by Konkan Railway Corp. Ltd. 5. “Project Report on critical study of Ballastless Track of Kolkata Metro Railway” by V.K. Verma 6. “Ballastless Track: Design, types, track Stability, Maintenance and System Comparison” by Dr. Ing. Edgar Darr 253
BALLAST - LESS TRACK TECHNOLOGIES - UNDERSTANDING THE GENERAL PRINCIPLES BEHIND DESIGN, FEATURES OF POPULAR SYSTEMS, AND PLANNING FOR INDIAN CONDITIONS Sri Surendra Kumar Shrivastav, IRSE, FIE(I), FIPWE (I), FIIBE (I), MICA Chief Engineer, SCRly Sri Hansraj Sharma, IRSE, Dy Chief Manager / IT / East Coast Railway Sri Ashutosh Kumar Shukla, IRSE, Dy Chief Engineer ( Bridges) / East Coast Railway
_______________________________________________________ Background and Introduction: As far as Adopting Ballast-less Track Technology is concerned, the country is almost on the verge of a similar situation that had happened when there was a nation to be made and a Constitution was required to create the general principles. Leaders who were set upon drafting the Constitution went abroad and studied all possible Constitutional systems. Thereafter, they had recommended something which was acclaimed to be the best out of all the Constitutions combined. We don’t necessarily intend to produce a parallel or recommend anything close to that, but we would definitely like to provide an overview of all possible Ballast-less manifestations of track in this world, so that our Decision makers can strategize upon the technologies that would be required. Our Paper is primarily an effort to lay down the understanding of those principles which work behind ballast-less technologies. By trying to do an analytical dissection on the plethora of technical details available, and by trying to limit the Mathematical and Figurative details to the minimum, we have churned out a subjective narration that would not be impeded by figurative descriptions or hindered by way of disjointed details, and help us focus on popular 255
technologies that could be adopted and customized for our purposes, rather than having to re-invent the wheel. This paper is also an effort to enthuse some proactive thought into the Tendering Process for Ballast-less tracks so that we end up with a project that we can be proud of. Classification of Ballast-less track Systems: Let us think in terms of Logical Layers, which are more understandable and intuitively appealing to our faculties. First Logical Layer being the Type of RAIL SUPPORT, systems can either be DISCRETE (point supported rails) or can be CONTINUOUS (all along supported rails). For DISCRETE Systems: (2 Sub Layers) • First Sub Layer being the Type of SUPPORT Material used, systems can either be CONCRETE or ASPHALT. • Second Sub Layer being the Type of SLEEPER and its SUPPORT, systems can either be EMBEDDED, PLACED on TOP, PRE-FAB or MONOLITHIC. For CONTINUOUS Systems: (1 Sub Layer) There can either be an EMBEDDED Rail or there can be a CLAMPED and CONTINUOUSLY supported Rail. There are several specific requirements that need to be addressed before the design and construction of a slab track. These requirements are shaped mainly in accordance with the ground conditions, the chosen slab track design, the supporting layers underneath the slab, the location to be build such as in a tunnel or a 256
bridge where most transition points are met, the materials, the traffic, the load per axle, noise restrictions, level of maintenance, construction costs, weather conditions, signaling and electronic systems to be used as well as passenger comfort. Let us take the first most important property of any such System. Table below gives details of the relative Flexural Stiff nesses that can be achieved in each of these systems: Ballast-less Track System
Flexural Stiffness
Lo
Hi
Blocks EMBEDDED in Concrete Sleepers on TOP of Asphalt PREFAB Concrete Slabs MONOLITHIC Designs EMBEDDED Rails CLAMPED CONTINUOUS RAILS
By doing similar comparisons for each of the design requirements, decision makers would have an excellent grip over the technologies to be adopted, suiting each of the location where ballastless track is desired. However, before we do such an exercise, it would be better if we could narrow down our list to the prevailing popular systems. Here’s a list of all the possible Ballast-less Slab Systems classified into Logical Layers as stated above:
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Ballastless Track System
Names of the Systems
Blocks EMBEDDED in Concrete
Rheda, Rheda Berlin, Rheda 2000, Zublin, Stedef, Sonneville –LVT, HeitKamp, SBV, Wallo
Sleepers on TOP of Asphalt
ATD, BTD, Sato, FFYS, Getrac, Walter
PREFAB Concrete Slabs
Shinkansen, Bogl, Obb-Porr, IPA
MONOLITHIC Designs
Rasengleis, FFC, Hochtief, BES, BTE - BWG /Hilti , Pact
EMBEDDED Rails
Deck Track, Infundo-Edilon, BBERS
CLAMPED CONTINUOUS RAILS
Cocon Track, ERL, Vanguard, KES, SFF, Saargummi
These Details can be difficult to parse. To make it simpler therefore, we have shown those systems in RED and in BOLD which have an operational length of 1000 Kilometers or more. By doing this exercise, we have been able to zero down our focus upon just two technologies, and 4 systems, out of the 34 available systems! Armed with this information, we can take a look into the distinguishing features of each of these 4 systems in a little detail, so that we can understand better what the other countries have been doing so far. The Rheda Systems: Rheda originated from Germany and the name is derived from the location where it all began. Features common to all Rheda Systems are: o Encased concrete sleepers (encased in concrete) o Sleepers have the same length 2.6 m (for monoblock variants) 258
o Adjustments to the track geometry are achieved by vertical and horizontal adjustments. o The Rheda systems rest on a hydraulically bonded layer (HBL) 30 cm thick and a frost protection layer (FPL) approximately 50 cm thick. o The minimum concrete quality for the concrete slab is C30/37. o The overall heights of the various Rheda designs are between 830mm and 961 mm (rail top to the top of the FPL). Further, Rheda Systems have been riding on a popular wave and have been adopted in Europe and Asia equally for the following reasons: o Rheda System is very flexible, allowing for design changes and enhancements in order to fit the demands of each location. Hence it can be found in tunnels, bridges, as well as on earth structures. o It has Uniform system architecture in all variants. o There is an Improvement of the monolithic quality. o Design optimization is possible. o Integrated techniques for slab track installation have been developed, moth for manual and automated. o It is OPEN SOURCE. The Rheda design is free of any patent rights, thus, since its birth it has been under continuous development by various contractors and many different structural versions have been created to fulfill different specifications in various projects.
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Image above and below show broad details of the RHEDA 2000 variant. Specifications shown in the image are of EUROPEAN origin. A Rheda system could similarly be developed for Indian Conditions.
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What can be done with this awareness ? A similar architecture could be standardized adopted for Indian Conditions. Scope exists for designing the following components : • Design of the Monoblocks in terms of Dimensions, spacing and Concrete Quality • Design of the Lattice Reinforcement in terms of cross section • Decision about the fastening systems • Design of the supporting framework / formwork for achieving desired geometry • Design of the Concrete Layer - The Hydraulically Bonded Layer and the Frost Protection Layer, if any Since we have RDSO as an arm that is equipped with all the requisite skills and resources to create designs, and standardize, we could have our own Menu for the Rheda System in India. Further, there could be separate drawings for Bridges, for Tunnels, and junctioning arrangements at Station Yards where Ballasted Track may still have to continue. The Sonneville-LVT (LVT = Lo Vibration Track), Stedef and Wallo Systems : Sonneville-LVT (Swiss) , Stedef (French) and Wallo (Swiss) Systems belong to one category of technologies where Design Principles and Construction Techniques are similar, i.e. a resilient Pad is placed under the Sleeper, encased fully in a rubber boot, providing high flexibility, and high protection against noise and vibrations. The whole Boot alongwith sleeper are embedded in poured Concrete. It is easy to repair such track because the sleepers can be taken out. Ingres of Water however remains an issue. Fastening System is Vossloh W14 / Pandrol E Clip/ Sonneville S.75. 261
This system is existing in the world famous CHANNEL TUNNEL / EUROTUNNEL. It is therefore a system that is proven for Tunnels, and all those locations where Derailments cannot be afforded.
Figure above shows the General arrangement of a Sonneville LVT system.
The Shinkansen Systems: This is a well known technology from Japan, and has been one of the oldest in the field (since 1972). This is a Prefab Technology. Prefab pre-tensioned slabs of approx 4.9 m x 2.34 m x 19 cm (5 tons each) are laid separated by concrete cylindrical dowels, and bearing plates are fixed onto the slabs, which hold the rails. Bitumen is also poured in between the slab and the Hydraulically bonded layer. Now Slabs have been developed with voids in between that make them lighter. Depth has been increased to allow pre-tensioning. This is a proven technology, and is customizable too. Construction technologies and Maintenance Processes too have been stabilized in this system. 262
Figure below shows the general arrangements of a Shinkansen System.
The BOGL system: This is a German technology. It is a prefab prestressed system. Each Concrete plate is approx. 6.45 m x 2.8 m x 20 cm and can weigh upto 10 tons. Special GEWI wires are used for longitudinal reinforcement. Slabs are designed with breaking points in between, to prevent random cracking. It looks like flattened sleepers joined together, back to back. Handling Equipment is specially designed to fasten these sleepers. The whole process is patented like Shinkansen or Sonneville LVT. It ensures excellent quality but the costs of transporation need to be weighed against this benefit. The joints are all sealed with concrete / bitumen.
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Images above show the BOGL system
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Conclusions: It is seen that except RHEDA, all other systems are patented and require import of technologies, be it construction methodology or the Fastenings. In a RHEDA system however, we need to import only the Fastening system. Other aspects of design construction and maintenance can be worked out within our own organization. It is also time that we standardised our general drawings of Ballast-less tracks for straights, curves, TUNNELS, BRIDGES and all interface locations, recognizing the peculiarities and inherent advantages of each system . We recommend RHEDA systems for Straights and curves, Sonneville LVT System for Tunnels, BOGL systems for Bridges, and Shinkansen systems at interface points. In case existing Lines are converted to Ballast-less track, Speed Potential, Maintainability and Interfaces at Level Crossings are areas which need consideration. Ballast-less tracks have a huge inbuilt capacity to upgrade Speeds. Other than Washable Aprons, Tunnels and Bridges, they should be planned in stretches where speed is an essential requirement from the customer’s perspective. Since Maintainability involves a rethink on existing practices, it is desirable to have modern Training Institutions capable of imparting such skills. Since we have at least one LC every Block section, at all such LCs, the existing Roads have to merge into the Ballast-less track in such a way that traffic capacities do not get choked. We therefore recommend grade separated Crossings in all Ballast-less track locations where the road traffic has to move across the railway line. Such Grade Separators shall essentially be minor bridges so that the Ballast-less track does not have to undergo a transition at every LC. These drawings can be standardized at RDSO. Uniformity in Architecture will always result in economical and speedy maintenance.
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Regarding Sleepers, the existing Sleeper Factories can seek permits to manufacture the sleepers for Special locations like Tunnels / Bridges, and for RHEDA System on curves and straights, RDSO can develop it’s own designs. Rails can be the same, but our Welding practices and Maintenance Practices have to change. We may need to have special Flash Butt equipment to carry out Joints in such Tracks. We may have to seek help and assistance from agencies abroad. From the tender documents of similar works being planned in our country, we feel that specifications for works need to be created to suit the various technologies till the time the standard codes come up for these purposes. Customers will definitely get a better deal as far as journey is concerned, but railways will have to re-organise their maintenance practices to suit customer expectations and technological requirements. In short, we need to go global only in certain areas if we are to adopt this technology. With depleting resources of good quality ballast, it’s not a faraway consideration to be made. Silver lining is that we CAN evolve our own flavors of Ballast-less systems, and grow along with the world, together and even better. Acknowledgements : We are greatly indebted to our Seniors in the Profession, without whose encouragement and constant support, we could not have embarked upon the task of writing this paper.
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BALLASTLESS TRACK ON EARTHWORK, BRIDGES AND TUNNELS THE SPECIFIC PROBLEMS ENCOUNTERED AND VARIOUS CONSIDERATIONS IN ITS DESIGN Pankaj Kumar Singh, Sr D E N / Co-ord / E. Rly / Asansol __________________________________________________________________________
Abstract: This paper discusses specific problems encountered by ballast less track on earthwork, bridges and tunnels. It also discusses patterns of development of structural design in different countries along with functional requirement to be kept in the selection of a particular type of ballast-less track structure. 1.0 Introduction: Development of ballast-less track has varied in its structure and form across the world due to the different development requirements and backgrounds. In Japan, the slab track was typically laid on the solid foundation such as a bridge or tunnel at first, and then it gradually developed to be laid on the soil sub grade afterwards. It adopts design as unit slabs. The German ballast less track was first laid on the soil sub grade and then on the bridges and tunnels. Its continuous structure involves the consideration of thermal effects. The early ballast less track in China was mainly laid in tunnels with the chief concern being the influence of train load. With the increasing application of ballast less track, a relatively general design theory and a structural system have been gradually formed after the innovative research with high-speed railway ballast less track. In India, Ballast less track has initially come in Sub-urban Metro system of Kolkata and Delhi. It is also being used in ballast-less track of washable aprons. However, with proposals of High speed Routes, Ballast less 267
track is likely to be introduced in High Speed routes under consideration. 2.0 Types of Ballast less Track The following types of ballast-less tracks have been adopted by various world railway systems on their high-speed tracks. i) Slab track based on the design adopted on Shinkansen, Japan: Japan was effectively the birthplace of high speed rail. Development work on the Shinkansen network started at the end of the 1950s, and the first line (between Tokyo and Osaka) opened in autumn 1964. Five lines are currently in service and a sixth is under construction. Government plans dating back to 1970specify a national Japanese high speed network of 3 500 km of double track. By 1993, a good 1400 km of this had been built (double track), of which more than 1000 km consists of ballast-less double track. In Japan, ballastless track always consists of prefabricated slab track, using slabs just under 5 m long. The percentage of ballast-less track varies considerably from line to line. The newer lines include a higher percentage (up to96%). The slab track design has remained virtually unchanged since the first sections were laid in 1972.The Shinkansen slab track, consists of a sub-layer stabilized using cement, cylindrical “stoppers” to prevent lateral and longitudinal movement, reinforced pre-stressed concrete slabs measuring4.93 m x 2.34 m x 0.19 m (4.95 m x2.34 m x 0.16 m in tunnels) and bituminous cement mortar injected under and between the slabs. The slabs weigh approx. 5 t. The rails are fixed on the top slab with standard KAWA type fastening system, having a rail-pad and also an elastomeric pad under the base plate. The rail fastening system allows considerable scope for vertical and lateral adjustment. The cement maxphalt mix layer can be suitably adjusted to accommodate any settlement of formation.
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South Korea is currently building a high speed line to link the capital, Seoul, with the port of Pusan. As in Japan, the line will include both ballasted and ballast less track. Similar system with certain modifications has been evolved by M/s Max Bogl called “Slab track system FF-Bogl”. Italian and Chinese railways have also evolved a similar system for their high-speed lines. ii)
REHDA Ballast-less Track System:
In this system, the sleeper with ordinary reinforcement (without pre stressing) together with the concrete bed that encloses it, constitutes a homogenous ballast-less track structure. Various versions of REHDA system have been developed. The latest among them is REHDA 2000. The REHDA 2000 is installed as a top-down system, with the help of service rails. The sleepers are assembled together with the rails to form a track framework, which is installed at proper position with the use of a special adjustment mechanism. The track-supporting layer of concrete is poured only after final alignment and levelling. This system has been used on a number of new highspeed lines in Germany. Recently, it has also been used in the station areas for turn-outs installation on Taiwan’s high-speed line. iii)
Stedef System:
The Stedef system, is most often used in tunnels. Metro systems are the most common application, but the technique is also used on high speed networks. A rubber boot under the sleeper provides a high degree of elasticity, which ensures good noise and vibration insulation. iii)
Low Vibration Track (LVT) System
LVT System developed by Roger Sonneville is similar to Stedef system. It comprises of concrete blocks, resilient pads placed under the blocks and rubber boots encased in a second pour concrete. The rails are fixed in position with the concrete blocks 269
adopting the standard French Nabla elastic clips. Pandrol, Vossloh or other similar elastic fastening system can also be used. No adjustment is possible in the position of concrete blocks after the second pour concrete. This system has been found true to its reputation of allowing very low vibrations from the railway tracks to adjoining structures. The system has therefore been extensively used on railway tracks in tunnel including the channel tunnel and also the tunnels on the Taiwan high-speed lines. iv)
Swiss Walo System
Another twin block variant related to Stedef is the Swiss Walo system, mainly used in tunnels. A special slip-form paver lays a concrete slab, following which the sleepers – fitted with rubber boots – are placed in position and cast into place. The Edilon block track system falls into the same category, and is mainly used for bridges and tunnels. Under this top-down system, the first step is to place the rails and blocks in position. The blocks are then cast in using Corke last, to provide the necessary elastic resilience support. Important applications include 100 km on NS and light rail systems in the Netherlands and the Madrid metro ( approx. 100 km ) iv)
Solid Slab Track-System NBO:
The solid slab “track-system NBO” is similar to the paved concrete track evolved in UK, sometime in 1970’s, where a specially designed concrete paver was used to lay the concrete slab to close tolerances. In the NBO system concrete paver leaves a groove in which rails with their elastic fastening system are accurately placed, adopting top-bottom construction technology. This system does not use sleepers and has the following main features: 1)
Concrete slab laid to tight tolerances
2)
Laying the rails complete with fastenings
3)
Use of rapid hardening grout (jointing compound) 270
This system, which is patented by M/s ThyssenKrupp, has been approved by the Technical University of Munich, Germany and has been laid on some high-speed lines in Germany and in South Korea. v)
Edilon Embedded Rail System
In this system rails are embedded in position with a suitably formulated elastomeric compound, which provides the necessary degree of elasticity. This system is similar to the “NBO” system, where a concrete pavement is constructed leaving grooves for the installation of rails. This system, although free from fastening component, has little scope for rail adjustment. Technical University of Munich, after carrying out necessary laboratory tests, has cleared the system for adoption on high-speed tracks. This system has been adopted by Taiwan on their high-speed lines at Taipei station. With limited scope for adjustments in the ballast-less track assembly, such tracks are best suited for locations where there is no or little possibility of settlement. Viaducts and tunnels are therefore the preferred locations for ballast-less tracks. However, on account of the advantages that ballast-less track offers over the ballasted track, they are being increasingly adopted in earth formations. In such cases, the sub grade structure is properly designed to ensure minimal settlement of the track during service. 3.0 Specific problems of ballast-less tracks on earth work 3.1 The ballast-less track on earthwork developed later than the BLT on bridges and in tunnel sections, as Earth sections show large settlements and ballasted section was considered better to adapt better to these large settlements. 3.2 The soil support (cutting or embankment) is constituted of economic materials from local source. Its mechanical properties of bearing capacity and sensitivity to frost affect its load bearing capacity. In general, these properties are insufficient to receive a level 271
of loading under track (ballast or slab).Therefore, in general there are sub layers of materials constructed with controlled properties having bearing capacity greater than 120N/mm² a height of 70 cm for the protection from frost. These foundation layers are practically a common element to ballasted tracks and ballast-less tracks. 3.3 In a ballast-less track like Rheda type (monolithic concrete) one finds a 30 cm layer of gravel treated to the hydraulic binding material. The intermediate structure of a trough with concrete infill brings a thickness of about 25 cm under sleeper. The height above the foundation levels are therefore the same order that in ballasted track. Concrete being more expensive than ballast, this type of track is necessarily more, expensive than a ballasted track. Reductions of thickness can be achieved by replacing simple layers of concrete by re inforcedor pre-stressed concrete sized for bearing and for thermal shrinking. For example, Stedef of Neuilly in France have laid prestressed slab sunder sleeper of thickness18 cm and 7 cm on embankment. 3.4 Globally, structures of ballast-less tracks appear to be oversized. They are designed for life spans of generally 60 years.In ballasted tracks, the structures are flexible and therefore can tolerate the settlement of the soil support. Also, corrections of geometry due to the settlements of the soil support is practically negligible in relation to corrections due to ballast deformation itself. As a matter of principle track structures of ballast-less track is a system which does not have inherent systematic geometry correction during the cycle of life; therefore they have more demanding requirement of bearing capacity than required in ballasted track. 3.5 The ballast-less track doesn't admit large settlement of the soil support. It is, therefore, imperative that the settlement of embankments newly constructed is nearly completed at the time of laying ballast less track. If this condition cannot be achieved, ballastless track on such earthwork should not be laid. Also, layers of longterm compressible soils must be removed in doing the earthwork. 272
3.6 Adjustable fastening systems should not be used where continuous long-term settlements is expected in foreseeable time frame. As foundations of railway-bridges are by design less susceptible to settlements than embankments around, one should adopt special arrangements to over come transitions between railway-bridges and earthworks. 4.0 Specific problems to ballast-less tracks on railway bridges 4.1 Separation of track and bridge structure: A first fundamental choice concerns the independence between bridge structure and track structure. One observes an important gap between a typical choice of metallic bridge optimised on the acoustic plan with integrated embedded rail for which that the type of track cannot be changed during all the duration of life of the bridge, and the choice to construct a railway bridge for a very important duration of life independently of the type of track for which one wishes to have the possibility to choose the type of track and to change it knowing that the duration of life of the track is much lower than that the bridge. For important railway bridges made of reinforced or prestressed concrete, a very wide spread problem consists in holding the upper slab of the bridge tightly and to construct above it track structure in simple support on this. This leads generally to a first distribution slab of the track including stoppers for transmission of horizontal effort to upper levels of the track including rail fastenings. 4.2 Electrical Insulations: For metallic bridges only, questions of tightness doesn't matter; on the other hand problems with electrical insulation between rails have to be particularly taken into account. 4.3 Fastening Systems and expansion joints: The ballast-less track will require fastening systems with lower resistance to longitudinal sliding. Also, the choice of the ballast-less track may lead to more rail expansion joints than with ballasted track while using standard fastening system 273
4.4 End Deformations: The limitation of the deformation of end of railway bridges (rotation of ends and uplifting of parts beyond bearings) that is desirable in ballasted track becomes more sensitive in ballastless track and must imperatively be covered by design rules. 4.5 Deflections: Admissible deflections of spans are linked to the comfort of passengers and design of counter flexure. The alternative of adjustable fastening system to counter deflections is recommended. 4.6 Transitions between railway bridges and earth works: Transition structures that are recommended in ballasted track layout become more critical in ballast-less track layout and must be covered in the design process. These considerations will be dependent on the nature of the filling behind the abutments, probability for the possible interruptions and the anchorage of slabs supporting the track. In principle the stiffness of a ballast-less track is mainly controlled in the structure of track; therefore there should be no problem with stiffness transition but only problems with differential settlements and deformations of extremities. The necessity to have adjustable bearing for railway bridges to compensate settlement of bearing is not generally applicable and but may be required in particular cases. 5.0 Specific problems related to ballast-less tracks in tunnels 5.1 If the tunnel has a raft, the laying of track in tunnel is easy. Supporting layers can be reduced and limited to having proper interface to obtain the final geometry. The design has to be obviously geared to take into account particularities of drainage systems or electrical cable passage, if necessary or other equipment. 5.2 The choice of a ballastless track instead of a ballasted track reduces maintenance effort to the strict minimum. The technological choice of the type of ballastless track can be linked to policies 274
concerning safety and especially possibility of circulation for rescue vehicles. 5.3 The overall dimension can also orient the choice of some solutions. Management of gauge during maintenance is easier with ballastless track than with ballasted. 6.0 Specific problems related to ballast-less track switches and crossings 6.1 For switches and crossings layout in ballastless tracks, the alternative technological solutions are limited than for the plain track. Solutions as embedded rails cannot be used for switches. Three orientations are possible, which are given below. 6.2 The first solution consists in taking a switch or crossing designed for ballasted track and simply to adapt bearers to realise a layout of supports on a resilient level (for example rubber booted bearers). 6.3 The second consists in adopting fastenings (intermediate track plates, sliding chairs of switches or supporting crossings) possessing a typical stiffness of ballastless track and to lay them on a slab. In the last case the difficulty to obtain the geometry of all rails is again greater than for plain track and the most reliable construction solution remains the use of prefabricated support (including the positioning of the cast in parts) to incorporate in a concrete slab. 6.4 The third consists in taking a switch with resilient fastenings, to put it on prefabricated slabs with a possible resilient level under the slabs. 7.0 Problems of Transition constructions Special transition constructions are required: -
between ballastless track and ballasted track 275
-
between two different types of ballastless tracks (for stiffness transition)
-
between plain line and switches
-
between bridges and plain track.
8.0 Secondary problems 8.1 Interfaces with the signalling: Track layouts have to take into account interfaces with the signalling and the overhead contact lines. It concerns mainly locations for equipment, of electrical connections to the rail, of insulation between rails and of possible ground linkage of metallic reinforcements. These problems have to be taken into account but do not constitute generally a criterion of choice of the type of track. The performance of insulation between rails is mainly insured by fastening systems 8.2 Problem of the noise: 8.2.1 Ballast-less track is generally noisier than ballasted track. For the problem of the noise one should distinguish the noise emitted by the track and the noise emitted by the rolling stock and partially reflected by the track. For embedded rail layout less mobility of rail can be compensated by difference in mass of the system ; for layouts on plates or with integrated sleepers the lesser mobility of sleepers compared to the ballasted track is probably compensated by a greatest mobility of the rail due to the fact of a weaker stiffness. 8.2.2 As far as the reflection of noise is concerned the ballast constitutes a good absorbent; its disappearance from the structure of track entails an aggravation of the reflected noise. One will find therefore in design of ballast-less track some ballast banquettes having a function of absorption of the noise and not for mechanical support. One can possibly have absorbent panels laid near rails ; this type of equipment constitutes a complementary option and is not really linked to a choice of structure for ballast-less track. 276
8.2.3 To contain the noise and vibration levels within acceptable limits, measures are taken, which include: adoption of floating slab, provision of noise barriers, rubber bearings, resilient base plates etc. taken on one of the railway lines with ballast-less track. 8.3 Problem of ground vibrations: 8.3.1 For the problem of ground vibrations improvements can be obtained as compared to the ballasted track either by using systems of track with suspended intermediate masses (rubber booted sleepers layout for example), or by adjusting the stiffness in systems with plates. In the last case, one should well verify the ability of fastening systems to accept unconventional stiffness. 8.3.2 Floating slab techniques suspended with resilient level can equally be used in conjunction with ballast-less track; one should then examine stiffness transitions at ends of these structures and the relative ease of replacement of the resilient levels under slab. 9.0 Considerations in design of ballast-less track: 9.1 Ballast-less track assemblies are expected to provide the same degree of elasticity in all directions as is available in ballasted track. This is necessary to contain the static and dynamic forces within acceptable limits. 9.2 In the design of Japanese slab track, the train load effect is a primary concern. Using the elastic design method, the security during the manufacturing, hoisting, and constructing of the slab track is maximized. As seriously damaged CA mortar at the slab corner and the slab warping caused by temperature gradients emerged, the uneven support caused by warping is considered in the analysis. In the base plate design, in accordance with the limit state method, the train load and the sub grade’s uneven settlement are considered together with the influence of weather conditions, concrete contraction, and construction. 277
9.3 German developed its ballast-less track by borrowing the design concept and method of pavement engineering. Most has longitudinally continuous structure, and temperature load and concrete contraction are the main factors to be considered in the design. The reinforcement is located near the neutral axis and does not bear the trainload. The effect of train load and temperature gradient is resisted by the rupture strength of the concrete. 9.4 In China, the early monolithic roadbed track, whose structure design mainly considers the train load, was applied in the tunnels with good foundation condition and little temperature variation. The structural design of the Suining-Chongqing railway took into account the effect of uneven foundation deformation and temperature load. Following systematic research on the ballast-less track, the design theory based on the allowable stress method was created with full consideration of train load, temperature, and foundation deformation effect. 9.5 In addition to above structural aspects, Ballast-less track assemblies are also expected to perform the following four important functions and design has to include these aspects also: (i) Dampen the high frequency vibrations of the rail. For that purpose, all ballast-less track assemblies have an elastomeric rail pad under the rail seat, on which the rail is expected to be under compression at all times. This is similar to the arrangement with the concrete sleepers in ballasted track. (ii) A medium to distribute the oncoming loads and absorb the energy generated, functions which are performed by the ballast in the ballasted track. This function is performed by incorporating an additional, comparatively softer elastomeric pad in the assembly. iii) Construction of track with close tolerances – It has to be noted that ballast-less track requires great precision during construction, as any change in level or alignment is difficult to be carried out at a later stage. 278
iv) Mechanization of construction - In developed countries, labour costs being very high, systems have been developed to mechanize the track construction to the extent possible. Pre-fabrication of track component is one way of reducing labour costs and for increasing the speed of construction. 9.6 In general, the design theory of ballast less track indifferent country was relevant to its own construction environment and structural evolution. The design theory proposed in different periods could meet the construction requirements for different types of ballast less track. Conclusion: In the above paper the various methods of construction of ballast-less track has been discussed. BLT face specific problems when being laid on different locations like earthwork sub grade, on bridges and on tunnels. Also, functional and structural aspects of design consideration have been given an overview. References: 1.
Esveld, C.: ‘Modern Railway Track’, MRT-Productions, ISBN 90-800324-1-7, 1989.
2.
Singh, K. P.: ‘High Speed Trains Around the World: Prospects for India’, RITES Journal, April 2000.
3.
Sanjay Misra: ‘High Speed Rail Transportation and its Indian Relevance’, RITES Journal, August 2007.
4.
Esveld, C. and de Man, A. P.: ‘Ballast-lesstrack for the High Speed Line South’ November 1996.
5.
Xueyi LIU, Pingrui ZHAO, Feng DAI:’ Advances in design theories of high-speed railway ballast-less tracks’, Journal of modern transportation, September, 2011.
6.
Marcel Fumey, Peter Zuber, et al, ‘Feasibility study- Ballastless track’, UIC infrastructure Commission, Civil Engg support group,2002. 279
Evolving Economical & Appropriate design of Ballast less Track - D.K. Chandrakar, DY CE BR I/CR __________________________________________________________________________
Synopsis Due to increase in urbanization in India there is a need for high speed intercity and intra city rail transportation. Also increase in traffic density is steadily making it more difficult to carryout track maintenance works. Ballasted track has its own limitations in speed as well as it needs frequent periodic maintenance; whereas ballast less track has a high speed potential & low or very little maintenance requirement. The present article deals with advantages of ballast less track and different propriety schemes followed world over with chief characteristics. Introduction: The track on a Railway or railroad, also known as the permanent way, is the structure consisting of rails, fasteners, sleepers and ballast (or slab track), plus the underlying grade. For clarity it is often referred to as railway track or rail road track. Not withstanding modern technical developments, the overwhelming dominant track from worldwide consists of flat bottom steel rails supported on pre-stressed concrete or timber sleepers, which are themselves laid on crushed stone ballast. Most railroads with heavy traffic use continuously welded rails supported by sleepers attached via base plates which spread the loads. A plastic or rubber pad is usually placed between the rail and tie plate where concrete sleepers are used. The rail is usually held down to the sleepers with resilient fastenings. For much of the 20thcentury, rail track used softwood timber sleepers and jointed rails. 281
The rails were typically of flat bottom section fastened to the ties with dog spikes through a flat tie plate in N America & Australia and typically of bullhead section carried in cast iron chairs in British & Irish practice. Jointed rails were used at first because the technology did not offer any alternative. However the intrinsic weakness in resisting vertical loading results in the ballast support becoming depressed and a heavy maintenance workload is imposed to prevent unacceptable geometrical defects at the joints. The joints also required to be lubricated and wear at the fishplates mating surface needed to be rectified by shimming. For this reason jointed track is not financially appropriate for heavily operated railroads. Hence now continuously welded rails are being used. The main advantages of ballasted type of track are: • Relatively low construction cost • High elasticity • High maintainability at relatively low cost • High noise absorption Disadvantage of traditional track structure is the heavy demand for maintenance, particularly surfacing (tamping) and lining to restore the desired track geometry and smoothness of vehicle running. Weakness of sub grade & drainage deficiencies also leads to heavy maintenance costs. Over time the ballast bed becomes less permeable due to grinding down of ballast, contamination and transfer of fine particles from the sub grade. Also ballasted track is relatively high, which has direct consequences for tunnel diameter and track access points. This can be overcome by using ballast less track. In its simplest form this consists of a continuous slab of concrete (like a highway structure) with rail supported directly on its upper surface using a resilient pad. 282
However ballast less track is very expensive in first cost and in case of existing railroads requires closure of the route for a somewhat long period. Its whole life cost can be lower because of great reduction in maintenance requirement. Ballast less track is usually considered for new very high speed or very high loading routes , in short extensions that require additional strength or for localized replacement where there are exceptional maintenance difficulties for example in tunnels. Rail traffic is reaching out towards new horizons on ballast less track systems. The arguments are indeed convincing: long lifecycles, top speed ride comfort & great load carrying capability. In many cases a maintenance free track system is the more cost effective solution over the long run. Advantages of Ballastless Track: Stability, precision & ride comfort Ballast less track assures a permanently stable track position & stands up to the great loads subjected by high speed train traffic, with performance characterized by top quality, functionality and safety. Millimeter-exact adjustment of the track system during assembly on the construction site is the prerequisite for great ride comfort in the train and for reduction of loads experienced by the rolling stock. Long life cycle & practically no maintenance with its service life of at least 60 years with little or no requirement for service or maintenance ballast less track offers great availability and unmatched cost effectiveness in high speed operations. Flexibility and end to end effectiveness in application with its comparatively very low structural height and with the possibility of achieving optimal required track position ballast less track technology offers highly attractive and beneficial solution as end to end systems
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technology for main track and turn out sections for applications on a uniform basis on embankments, bridges and tunnels. Basis for optimal routing of rail lines for high speed operations ballast less track technology enables more direct routing of train lines, with tighter radii and greater slopes. These benefits enable reduction or even elimination of costs & work for civil engineering structure. Efficient vibration protection by using 2 stage vibrations attenuation design effective vibration protection can be ensured. Increased speed and safety greater track stability results in higher speeds and reduced number of track maintenance operations and thereby increased safety. Ballastless tracks The development of ballast less track system started in the second half of the 20th century in Japan (due to high speed train traffic), A few years later these developments reached Europe. The Japanese developments focused on precast elements, but the developments in Switzerland were based on booted sleeper systems while in Germany, the developments were based on monolithic cast in place systems. There are a number of propriety systems and variations include continuous in situ placing of a reinforced contract slab or alternatively the use of precast pre-stressed concrete units laid on a base layers. Many permutations of design have been put forward. RHEDA 2000 R ballast less track system The monolithic, ballast less RHEDA 2000 system is used for mainline tracks, especially on high speed routes. Chief characteristics
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of the supporting concrete slab include its lack of a trough, and its use of a modified bi-block sleepers with a lattice truss. As a result of the monolithic structure of the track supporting layer and the low overall structural height this system is suited for applications for earthwork systems, tunnels and bridges including those designed for trains that run at speeds over 300 kmph.
The advantages of RHEDA system are: • Cost effectiveness and reliability by utilization of concrete sleepers as superior quality precast concrete building components in the critical area of the rail seat zone. • Great precision of track geometry parameters by application of precise concrete sleepers. • Adaptability to all types of substructure by means of application of cast in situ concrete track supporting layer. GETRAC system for concrete sleepers The chief characteristic of GETRAC track systems is of asphalt supporting layers on which concrete sleepers directly rest. The 285
sleepers are elastically connected to the asphalt layer by special concrete anchor blocks, which transfer the horizontal forces from the track panel to the asphalt. A major advantage is the fast and simple installation technique with conventional track laying technology & with high daily track laying output. The German Federal Bureau of Railways has granted its approval, without speed restriction to various track design.
Shinkansen BLT (Japan) Japan is effectively the birthplace of high-speed rail. Development work on the Shinkansen started at the end of the 1950s, and the first line (between Tokyo and Osaka) opened in autumn 1964. In Japan, ballast less track always consists of prefabricated concrete slabs, each just under 5 m long. The percentage of ballast less track varies considerably from line to line. The newer lines include a higher percentage (up to 96%). The ballast less track 286
design has remained virtually unchanged since the first sections were installed in 1972. The Shinkansen ballast less track consists of a sub-layer stabilized by means of cement, cylindrical ‘stoppers’ to prevent lateral and longitudinal movement, reinforced pre stressed concrete slabs measuring 4.93 m x 2.34 m x0.19 m (4.95 m x 2.34 m x0.16 m in tunnels) and bituminous cement mortar injected under and between the slabs. The slabs weigh approx. 5t each.
OBB / Porr System Slab Track System The OBB (Austrian Federal Railways) / Porr system was designed to replace the typical behavior of the ballasted track by several elastic elements in the ballast less system. The typical behavior of the ballasted track shows the elasticity in the ballast itself 287
and in the rail fastening system. These two elastic elements have to be copied by the elasticity of the rail fastening system in the ballast less track and of the elasticity of a second layer which is situated at the bottom of the prefabricated slabs. This system leads to a distribution of the elasticity between the elastic coating of the slabs and the rail fastening system of 10% to 90%. Usually, the rail fastening system of IORV-300-I from Vossloh realizes the needed elasticity in the rail fasteners. The elastic coating consists of a PUR bound granular rubber. During train operations this leads to rail deflections of 1.5 mm under a Taurus Locomotive (about 22.5 tones axle loads). The main advantages of the system are: •
Very small space needed ( width of slab is 2.40 m and can be reduced down to 2.10 m, thickness of slab is 16 cm, which leads to a construction height of 50 cm. from top of rail down.
•
Use of standard rail fastening system vossloh IOARV-300-I which makes an easy maintenance possible.
•
Very good vibrating attenuation performance ( the system can be addressed as a floating track slab system with about 1 ton/meter sprung mass)
•
Simple construction procedure on site because of use of only few concrete on site ( most of the fabrication is done at the prefabrication site)
•
Easy & effective repair concept ( exchange of rail fastness or whole slabs can be done very easily in very short time)
•
Nearly no regular maintenance work necessary.
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Sonneville low Vibration Track (LVT) Ballast less slab system The LVT system consists of a concrete block, a resilient pad and a rubber boot, surrounded by unreinforced concrete (2nd stage concrete).No special demands on rail fixation are made; merely an elastic rail pad is used. For each specific project, these two elastic components are matched to each other, thus bestowing upon the system the properties characteristic of dual-level elasticity. The resilient pad provides for the load distribution analogue to the ballasted track and reduces the influence of low frequency vibrations. The rail pad in turn protects against the effects of higher frequency. The rubber boot allows an unhindered deflection that, together with the high quality of the resilient pad, leads under dynamic loads to very low system stiffening. All necessary functions for the track are taken over by the decoupled concrete block. This reduces the demands made on the 2nd stage concrete. The LVT can be tailor made for each project depending upon requirement like for high speed, heavy haul or for high attenuation. LVT is a better, versatile and a more cost effective system. Already over 1000 K.M. of ballastless track has been constructed using this technology and has been successfully running for the last 40 years. This system has been in use satisfactorily in three of the four largest tunnels (including channel tunnel) in the world and on viaducts on crowded cities such as London.
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SONNEVILLE LVT 290
This system has several advantages and most importantly the following: 1.
It is not restricted to one fastening system. It can be used with Indian railway fastening system such as MK III and MK V elastic fastening system and also with e-clip, Pandora Fast Clip, W-14 clip or any type of Vossloh fastenings and others. 291
2.
It has been used for 15-36 tones axle loads, for speed up to 280 kmph, in grade up to 5% and radius of curvature of 119 meters.
3.
It has exceptional vibration attenuation, lateral resistance and dynamic gauge control due to the deep embedment of the wide concrete blocks in the track concrete.
4.
It enables unobstructed central portion providing a safe walkway for maintenance workers and easy access for cleaning.
5.
This system is a versatile system which can be installed in normal track and in turnouts, at grades, in tunnels, on viaducts or bridges, or on concrete aprons.
6.
It can be used for light rail, metro, passenger and freight traffic and accordingly tailor made.
7.
Accurate track geometry is ensured due to the top down construction method.
8.
There are no exposed steel components that may be corroded in course of time.
9.
There is no direct electrically conductive link between the opposite concrete blocks as with some other system.
10.
A high installation rate of about 300 meters in 10 hour shifts has been achieved with this system
LVT system would suit for construction on viaducts, in tunnels, on aprons and others. The Stedef system It is most often used in tunnels, with metro systems being the most common application. This technique, however, is also used on high-speed track. The rubber boot under the sleeper provides a high degree of elasticity, which in turn ensures good noise and vibration insulation. 292
The Swiss Walo system Another twin –block variant related to the Stedef system is the Swiss Walo system, which is mainly used in tunnel. In this case, first a special slip form paver lays a concrete track base and installs a cable duct. Then the twin-block sleepers – fitted with rubber boots – are placed in position and cast into place.
The Edison Block System Mainly used for bridges and tunnels, falls into the same category. When installing this ‘top-down’ system. First the rails and blocks are placed in position. Then the blocks are cast in using Corkelast, in order to provide the necessary elastic support. 293
The embedded rail constructions All the ballastless track designs mentioned so far are based on the rail being supported at discrete points – the sleeper principle. Since 1976, a continuously supported rail system has been in use – on a small scale – in The Netherlands. This system, which is known as the Embedded Rail Construction (ERC) provides continuous rail support by means of a compound consisting of Corkelast, a cork/polyurethane mixture developed by Edilon BV. The great advantage of this design is that the track is built ‘topdown’, which means that tolerances in the supporting structure have no effect on the track geometry obtained. NS now has 20 years of experience with this system. It has proven to require little maintenance. Conclusions: Conventional track, using ballast, has been the norm for a long time. Over the years, there has been a movement away from timber/steel sleepers in favour of concrete. This is primarily due to the superior dimensional stability, longer service life and greater stability of concrete. Modern track with sleeper appears to be very suitable for high speeds and for heavy freight traffic. Low construction costs and ease of maintenance are essential, positive factors. In combination with a sound subgrade and reinforcing layers of, for instance, bituminous concrete, sleeper track will remain an attractive concept well into the 21st century. For new main corridors for high-speed and freight traffic, factors such as extended service life, low maintenance, availability and capacity for increased speeds and axle loads will gain in importance. Ballast less track designs offers certain advantages in this respect.
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BALLAST - LESS TRACK DESIGNS FOR MAINLINES, METROS AND AT WASHABLE APRONS - J S Mundrey (Formerly Advisor, Civil Engineering, Railway Board, India) __________________________________________________________________________
1.
Evolution of ballast-less track
In the rail history of 150 years, ballast has been an important constituent of railway track. Over the years, many techniques have been adopted for improving the geometry and maintainability of the ballasted track structure. They include, inter-alia, design and construction of formations employing state-of-the art geotechniques, introduction of blanket layer, increased ballast cushion, adoption of concrete sleepers, use of elastic rail to sleeper fastenings, continuous welding of rails and adoption of mechanized maintenance system. With these measures, there has been considerable improvement in the track geometry standards and in the service life of ballasted tracks. However they still need continuous surveillance and timely attention, to ensure the desired degree of comfort and safety. In the conventional ballasted track, impact forces from the rolling stock are absorbed by the elastic deformation of the ballast and the formation underneath, approximately, 50% by each of them. In the ballast, the forces are absorbed by way of a change in composite contact relationship among the ballast particles. This change is partly cumulative in nature. The major part of the track maintenance work consists of correcting the surface geometry by rebuilding the deformed ballast. Unless ballast is replaced by some other material, having truly elastic properties, the track will need periodic monitoring and maintenance. The formation underneath also does not behave in a truly elastic manner and undergoes a plastic change. The track levels are therefore required to be brought up by increased input of ballast. To make the permanent way, a reasonably permanent in nature, ballast-less track systems have been evolved.
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In the ballast-less track, the track has to rest on unyielding foundation which could be of rock, concrete or well designed compacted soils. In ballast-less track, the elastic characteristics of the ballasted track are simulated by providing suitably designed track assemblies in which elastomers play an important part. Such tracks do not require any maintenance, except in the replacement of elastic assembly components, after serving for their lifetime. Adoption of ballast-less track is particularly advantageous in tunnels and viaducts where concrete bed forms an integral part of the sub-structure. This gives considerable scope in the reduction of tunnel construction cost as ballast-less track allows for certain reduction in tunnel diameter. Similar scope exists in the construction of ballast-less track on viaducts. 2.
Advantages and disadvantages of ballasted track
Following table enumerate the advantages and disadvantages of ballasted track: Advantages
Disadvantages
Known and proven method, up to a speed of 350 Kmph
Track tends to move both vertically and laterally- requires frequent tamping
Low construction cost
uncompensated lateral acceleration due to limited availability of lateral ballast resistance
Availability of highly mechanized construction technology
Ballast churns up at higher speeds damaging rails and wheels
Good elasticity for efficient absorption of noise and vibrations
Elasticity gets affected with pulverization and contamination - periodic deep screening required.
Reasonably good maintainability with track machines
On ballasted deck girder bridges of highspeed lines, ballast deterioration is much faster.
Less sensitive to construction defects
In heavy rain-fall areas, track requires closer monitoring to guard against subsidence and washouts
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3.
Plus and minus points of Ballast-less tracks
Plus points
Minus points
High operational availabilitytime required for maintenance is almost nil
Comparatively higher construction cost, particularly when laid down on earth formation, about 1.5 times in tunnels and 2 to 3 times on earth foundations, compared to ballasted track
Long lasting geometry
Highly sensitive to construction defects
good
track
Long life of track structure, 40 to 50 years
Dedicated costly equipment needed for maintenance and renewal
Predictable behavior of track components and thus of track geometry, timely replacement of track components
Less absorption of sound radiations and vibrations
High resistance to lateral and longitudinal forces permitting steeper grade and higher speed.
Mechanization of track construction and renewals still in infant stage
Regularity of the rheological (transmission of electric current) properties
Restoration is difficult and time consuming after derailment
4.
Design Philosophy of ballast-less track
4.1
Ballasted track has elasticity in all the six directions. Ballastless track is expected to provide the same degree of elasticity, to dissipate the energy imparted by static and dynamic loads.
4.2
An ideal ballastless track is expected to perform the following two functions:
Dampen the high frequency vibrations of the rail. For that purpose, all ballast-less track assemblies have an elastomeric rail pad under the rail seat, on which the rail is expected to 297
remain under compression at all times. This is similar to the arrangement with the concrete sleepers in ballasted track.
A medium to distribute the oncoming wheel loads and absorb the energy generated in rail/wheel interaction, the function which is performed by the ballast in the ballasted track.
These functions are performed by different arrangements in the various ballast-less track assemblies, as brought out in the succeeding paragraphs 5.
Types of ballast-less track assemblies
5.1 Simple plate type ballast-less track assemblies used in metros: These assemblies have the following important components: a)
Rail
b)
Rail Pad
c)
A cast iron steel plate for load distribution
d)
Elastic rail clips
e)
An elastomeric pad of 10 to 12 mm thickness to function as ballast.
f)
Steel plates/stiff rubber pad for height adjustment.
g)
Anchor bolts with triple coil washers, to provide desired degree of fixity and elasticity
In these assemblies, upper rail pad dampens the rail vibrations, the lower elastomeric pad dissipates the energy imparted by rail/wheel interaction. While rail vibrates at over 1000 Hertz, the plate vibrates with its own natural frequency; heavier the plate; lower is its frequency and amplitude.
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5.2 Ballastless track assemblies having two cast iron plates. These assemblies have the following important components: a)
Rail
b)
Rail pad
c)
Upper cast iron plate to hold the rail elastically
d)
Elastic rail clips
e)
An elastomeric pad 10/12 thickness to function as ballast
f)
Lower cast iron plate to contain the above plate centrally in position
g)
Fastening arrangement to hold the two plates together elastically
h)
A lower stiff rubber pad for providing conformity between the cast iron plate and the concrete surface below and for height adjustment.
i)
Anchor bolts to hold the assembly in position.
In the two plate assemblies, the main elastomeric pad of 10-12mm thickness is sandwiched between the two cast iron plates. This arrangement helps to withstand the high level of vertical and lateral forces that get generated with heavy haul/high speed operation, more efficiently and effectively 5.3
Further developments in ballast-less track assemblies
Further developments in ballast-less track assembles have been in two considerations: a)
For speedy construction of ballastless track using plate type assemblies and also for better quality controls.
b)
For bringing down the vibrations level to the bare minimum. 299
In some of these assemblies, the plates are usually replaced by a concrete mass either in the form of concrete slabs or concrete blocks. Elastomeric pads or other elastic material is introduced under the concrete slabs/blocks. 5.4 ballastless track assemblies with rails enclosed in elastic olymers A number of ballastless tracks assemblies have recently been evolved where rails themselves are enclosed in elastic materials. Such simple forms of ballast-less tracks are being increasingly adopted to meet specific operational requirements of a railway system 6.
Factor affecting the choice of ballastless track design a)
Axle load.
b)
Permissible speeds.
c)
Track construction parameters, such as curves and grades
d)
Accelerating and braking forces transmitted to the track.
e)
Limits of sound and ground vibrations- proximity to residential buildings/sensitive areas such as operas, hospitals etc.
f)
Availability of hard unyielding base.
g)
Cost of initial construction, maintenance and replacement
h)
Availability of heavy machinery for construction and renewal
i)
Availability of adequate traffic blocks during construction on the existing railway lines.
300
7. Main types of ballast-less track assemblies- their merits and demerits 7.1. Single Plinth type ballast-less track assemblies presently in use in Indian Railways
Figure 1
M.1. (a) assembly adopted by Calcutta Metro (Figure 1) This assembly has the following components:
6 mm thick elastic rail pad
Mark 3 elastic rail clips
Cast iron base plate
12 mm thick elastic base plate pad
High tensile steel bolts screwed into high density polythene inserts
Triple coil spring washers
Eccentric insulating washers for insulation and lateral adjustment
Steel plates for vertical adjustments.
301
Merits and demerits Merits a)
Has all indigenously developed components
b)
Can be constructed by skilled manual labour. No major machinery required for construction and maintenance
c)
Not much problem of excessive vibrations/noise
Demerits a)
On sharp curves, bolt fixing arrangements creates problem
b)
Polythene inserts have relatively poor service life.
c)
12mm thick pads used have poor service life when compared to pads used on Delhi Metro.
7.2 Vossloh 336 ballastless track assembly adopted by Delhi Metro. (Figure 2) This assembly has the following components:
Figure 2 302
•
6 mm thick elastic rail pad
•
Vossloh elastic rail clips
•
Maleable cast iron base plate
•
10 mm thick elastic base plate pad
•
5 mm thick plastic pad for conforming and height adjustment
•
High tensile steel anchors, cast in concrete
•
Triple coil spring washers
•
Eccentric insulating washers for insulation and lateral adjustment
Merits a)
With top to bottom construction and well designed rubber pads, good quality track construction has been possible
Demerits a)
Except the MCI plate and anchors all other items are imported and thus costlier
b)
A large number of nuts are required to be tightened, problematic without a mechanized equipment
7.3
Logwell ballast-less track assembly proposed for Calcutta Metro
•
M/S Logwell Forge Ltd. have developed a ballast-less track assembly for metros which is a hybrid design incorporating the best features of both Calcutta metro and Delhi metro ballastless track assemblies. 303
Figure 3
•
It uses Logwell G Clip for fastening rail to the base plate having a toe load of 900-1200 Kg, equivalent to Vossloh clip. The base plate is anchored to the concrete in a manner similar to Vossloh design, thereby having a stronger fixing arrangement. The assembly has been provided with base plate pad 10 mm thick and plastic pad of 5 mm thickness similar to Vossloh design.
Merits a)
It is an indigenous design and thus more economical
b)
With a higher toe load, its hold on the rail is equal to that of Vassloh clip
c)
It has less number of components when compared to Vassloh 336; particularly the number of nuts to be tightened is reduced to 50%.
d)
It can be efficiently and economically constructed by adopting top to bottom system
e)
It has good scope for vertical and lateral adjustment.
7.4
Plinth type ballast track assembly for mainlines of Indian Railways (Figure 4, 5 & 6)
Figure 4. Vossloh System 1403 304
Figure 5. Pandrol Vipa System
Figure 6. Logwell Forge system 305
For mainline track, stronger plate type assemblies have been evolved. In these assemblies, two cast iron plates are used, sand witching the base plate pad between the two. The anchor bolts in these assemblies are not subjected to bending stresses and thus have much greater resistance against lateral forces. Pandrol Vipa System and Vossloh 1403 are such assemblies. M/S Logwell Forge has evolved an indigenous ballastless track assembly for main lines, LH- 1 incorporating the design features of the above mentioned assemblies. In this design, specially designed clips have been incorporated which exert optimum toe load of 300 kg, necessary for efficient functioning of the base plate pad. With top to bottom construction, the assembly provides a very efficient economical and durable track structures for heavy haul high speed lines. With LH-1 assembly, it is possible to provide checkrails wherever required. Main advantage of this system is that it affords quicker restoration of traffic after any derailment, when compared to more sophisticated systems. 7.5
Rhede ballastless track system incorporating Vassloh rail fastening system 300. (Figure 7 & 8)
Vassloh rail fastening system 300 is a miniature Vassloh 1403. It has the advantage that it can be incorporated in a concrete sleeper. The concrete sleepers can be mass manufactured in a depot and transported to the construction site to be laid in position with second pour concrete. This system affords a good quality track and speedy construction.
Figure 7
306
Figure 8
Merits a)
All construction work can be done mechanically-labour content for field works is much reduced
b)
Better quality control can be exercised
c)
Higher progress in track construction can be achieved
Demerits a)
Very heavy machinery is required for track construction
b)
Restoration of track is difficult and time consuming after derailments.
c)
Difficult to provide check railing facilities 307
7.6
Slab type assemblies (Figure 9)
In these designs, precast slabs of about 5 m long incorporating rail fastening assemblies are brought to the site. An elastic medium is provided between the base concrete and precast slab. Shinkansen (Japan) have cement maxphalt mix as the main elastic medium. Other such assemblies have their own patented materials. 7.7
Figure 9
Roger Sonneville twin block low vibration track (Figure 10, 11 & 12)
In this system, rubber booted independent concrete blocks for each rail, having an elastomeric micro cellular pad, are placed in position with second pour concrete. Standard concrete sleeper fastenings can be used for fastening rails to the concrete blocks
.
Figure 10 308
Figure 11
Figure 12
Merits a)
The system has the advantageous of transmitting very low level of vibrations’
b)
It has a long service life 309
Demerits a)
Heavy machinery is required for construction and maintenance
b)
Difficult to replace concrete blocks rubber boots/micro cellular pads
c)
Difficult to change the elastic properties of the track, the rails, often require periodical grinding
7.8
Floating track system with elastomeric pads (Figure 13)
Railway track whether ballasted or ballast-less is a source for vibrations which get transmitted to the adjoining structures. These vibrations often cause a lot of discomfort to the occupants particularly when the buildings are in close proximity. The situation becomes critical when the railway track passes through sensitive areas such as hospitals, operas, old archeological monuments etc. At such locations, floating track system can be adopted. In this system, concrete slabs carrying the track structure are supported on elastomeric pads or coil springs. A typical cross section of such a track is given in figure 13. In these types of tracks, vibrations coming from track get dissipated, with very little effect on the adjoining structures.
Figure 13 310
7.9
Rails embedded in elastomeric medium - Edilon Embedded rail system (Figure 14 & 15)
In these systems, the rails are held in position by a well formulated polymer. This, while holding the rail to correct geometry provides necessary degree of elasticity. During construction, grooves are left in the base concrete at appropriate location. The rails are placed in the grooves and elastomeric compound is poured around the rail. The compound not only provides the necessary fixity, but also the desired degree of elasticity. Such systems are now being increasingly adopted in station areas where they provide a cleaner environment, easy to maintain.
Figure 14
Figure 15 311
8.
Ballast-less track for washable apron of metropolitan stations in Indian railways
Design criteria of ballast-less track for washable aprons (i)
Should have a minimum number of steel components, as they would rust when frequently exposed to humid and toxic environment.
(ii)
Should be easy in installation, replacement and repair.
(iii)
Should be able to hold the track geometry within acceptable tolerances.
(iv)
Should have a long service life preferably equal to the life of the rail.
(v)
Should be able to contain the noise and vibration levels within acceptable limits.
(vi)
Should be easily washable, as human excreta from the carriages is likely to fall on the track. This requires the track assembly components to be as plain and simple as possible, causing least obstruction in the washing process.
(vii)
The washing of track may be achieved by directing pressure water jets to all the soiled places along the track. The pipes for this purpose may be located within the platform walls or concealed in low level concrete walls constructed between the tracks.
(viii)
The effluent generated from the washing of the tracks should get discharged into underground drains from where it will go to the recycling plants for making the water reusable for washing the platform lines again.
(ix)
The litter/garbage remaining unwashed should be picked by mechanical broom/vacuum cleaning machine which may be rail based and traverse the full length of the platform within a 312
reasonable time of about ten to fifteen minutes, much before the placement of the next train on the platform line. (x)
At the platform end, the machine should be able to get off the rails on its own and settle at a convenient location.
9.
Edilon embedded rail system best suited for adoption of washable aprons (Figure 16)
This assembly has the following advantages when used at washable aprons a)
It is easier to wash
b)
No Steel component other than the rail
c)
It is comparatively easier to install, replace and repair
d)
Its service life is claimed to be equal to the life of the rail. The system installed 25 years ago is functioning satisfactorily. Since then new and more efficient elastomeric rail in glues compounds have been developed.
e)
It has a good noise and vibration absorption capacity
f)
Embedded Rail reduces the rail level considerably, thereby bringing down the height of the platform. This is an important feature of this assembly for use on platform lines.
g)
The system has been adopted in many station yards such as Madrid (Spain), Amsterdam (Netherlands) and Taipei (Taiwan).
h)
The system has certification from Technical University of Munich
i)
Proper construction and maintenance manuals have been evolved by the user railways.
313
Figure 16
EDILON CORKELAST EMBEDDED RAIL FOR STATION
Case Station Length
Spain, Madrid, the atocha main line ave 8250 meters divided over 15 track 1992
Date Traffic
Axle loads up to 22 tones, maximum speed 80km/h
Construction:
Concrete slab with the Edition corkelast embedded Rail System
Remark
9.1
Termination station for High Speed AVE train Madrid – sevella the urban and suburban stations also have embedded rail
Limitation of Embedded rail system (Figure 17)
The embedded rail system has however one limitation. At breathing lengths, the rail holding polymer has limited capacity to elongate. Therefore, where the temperature variations are high, the breathing lengths are required to be located on the adjoining ballasted track structure, in continuation with the embedded rail system. Figure 17 314
9.1 Equipment for cleaning the track (figure 18 to 21)
M/s. Schorling Brock GmbH of Germany are in the business of designing and manufacturing, rail track sweeping and vacuum cleaning systems, for the last few decades. Some of the equipment manufactured by them is shown in Figures 18 to 21. They have shown considerable interest in designing a cleaning equipment for washable aprons meeting the design criteria mentioned in para 8 above. They Figure 17 will install their equipment on an Indian railway rolling stock. They propose to collaborate with an Indian company for the maintenance of their cleaning system.
315
Figure 18
Figure 19 316
Figure 20
Figure 21 317
10.
Ballast-less track system for high speed lines in India
For high speed lines on world railways, ballast-less tracks are being increasingly adopted. The choice of ballast-less track depends upon the location. The new high speed line recently completed in Taiwan provides the best example of selecting the right type of ballast-less track for various locations on that line. For example: a)
b)
c)
d)
On all viaducts and on grade track, slab type of ballast-less track, similar to that adopted on Shinkansen of Japan - figure 9. Apart from its long service life, with the least maintenance inputs, it has the possibility of good degree of vertical and later adjustments. In all tunnels Roger Sonneville LVT system- figure 10. Its low vibration track assembly does not allow track vibrations to go to the adjoining structures. On turnouts, Rhede system has been adopted- Figure 7. It provides the best technology in getting the right geometry on complicated layouts. At stations, embedded rail system- figure 14-15 it affords a clean environment at the stations.
We may follow the example of Taiwan high speed lines, when we construct high speed lines in India. 11.
Conclusions and recommendations
In conclusion, we may recommend as under: a) b) c) d)
Single plate assemblies as adopted in the metros of Calcutta and Delhi, provide the best option for all metros For main lines of Indian railways, two plate assemblies provide the best techno economic solution For washable aprons, embedded rail system is the best choice For high speed lines, the example of Taiwan can be followed where four types of ballast less track assemblies have been adopted, each best suited for a particular location. 318
DEVELOPMENT OF APPROPRIATE DESIGN OF BALLASTLESS TRACK FOR BANGALORE METRO RAIL PROJECT S. Parameshwara Iyer, Retd. CAO/S.Rly _____________________________________________________________
Synopsis: Ballastless track has, over the last two decades, got established as the standard track form for Metro systems in India due to its many advantages such as easy maintainability, less construction height, low maintenance cost, least impact on the environment etc. Its main advantage over ballasted track is that it is ballastless. The functions performed by ballast in ballastless track are assigned to track components in ballastless track, specially designed to perform these functions. In Bangalore Metro Rail Project, ballastless track has been adopted for elevated, underground and At-grade stretches of alignment. Design of track at each of these locations present unique problems. Since it is largely provided on elevated track, the impact of displacement and rotation of supporting girders on the stability of track introduces a new element in its design. An attempt has been made in this paper to bring out the various aspects of its design,as adopted in Bangalore Metro Rail Project, from the structural angle as well as its interface with signalling and Traction systems. 1.
Introduction.
The Bangalore Metro Rail Corporation Ltd. has progressed with the implementation of the Phase I of the Mass Rapid Transit System. The first Reach from Byappanahalli to M.G.Road, a length of 319
7.5 kms of double track electrified with 750Vdc third rail system was commissioned on 20.10.2011. The Phase I of the project is comprised of an East-West corridor from Mysore Road to Byappanahalli, approximately 18.1 km long with 17 Stations and a North-South corridor from Nagasandra to Puttenahalli, approximately 24.2 km long with 24 Stations. The two corridors traverse through the metropolitan city of Bangalore, on elevated viaduct, through underground tunnels, and at-grade sections. Each corridor has two tracks laid to Standard Gauge (1435mm) to cater to each direction of track and a maintenance depot, one each in the two corridors, at Byappanahalli and Peenya. The two corridors are interconnected for operational facility close to Kempagowda commuter interchange station. Power supply for traction is through 750V DC third rail bottom collection system. The track over most of the length is laid as ballastless track fitted with Elastic fastening system-336, on plinths/RC slabs. A small length of main line track at Byapanahalli and the track in Byapanahalli and Peenya Depots are ballasted. The Track is laid with EN 60,1080 grade HH rails to 1435mm standard gauge. The sharpest radius of horizontal curve is 120m on the main line and 100m in depots and other non-running lines. Minimum radius of curve in station area is 1000m.Minimum radius of vertical curve is 1500m. The viaducts are generally of standard spans of 22m, 25m, 28m and 31m, shorter spans being preferred for curved alignment. These are of segmental construction with end segments of 1.95m and intermediate ones of 3m. The non-standard spans are cast in situ, viz 45m, 50m, 56m & 66m. The underground portion of the alignment has four structural configurations. The approaches from the elevated track to underground is partly on viaducts and partly in open cutting, with a track spacing of 4.2m. The track spacing is increased from 4.2m to 320
15m using box sections. Further, the track is laid at 15.0m centers in two tunnels of 5.2m minimum internal diameter (external diameter being 6.1m) between stations. Island platforms serve the tracks at 15m centres in tunnels. Track in stations and box tunnels are laid on track slabs anchored to 150mm leveling course laid on bottom slab of the station/box structure. Track in circular tunnels are laid on track slabs laid on leveling concrete, the slabs being anchored for 100m at the ends of the circular tunnel. Track over viaducts are supported on track plinths. This paper deals with the evolution and design of the ballastless track used in the project 2.
Evolution of Ballastless Track
Ballasted track has certain limitations and problems such as deterioration of track quality with time, high maintenance input, frequent maintenance interruptions, ballast attrition and re-coupment etc. These problems are primarily related to the ballast as an elastic medium providing lateral and longitudinal resistance to track. Ballast quality deteriorates with time and so does its capability as an elastic medium absorbing noise and vibration and providing lateral and longitudinal resistance to track. There are certain applications where these disadvantages prove too costly demanding an improved track system. The solution has been found by means of replacement of ballast with another elastic medium, and supplementing it with devices to provide adequate lateral and longitudinal resistance. The result is the ‘ballastless track’. Ballastless Track has the following advantages over ballasted track • The track is practically ‘maintenance free’. Maintenance cost is 20-30% of that of ballasted track 321
• Low maintenance requirement, and hence high availability • Increased service life, and therefore large interval between track interventions for replacements and repairs. • Reduced structure weight and height. • Environment friendly-less dust, noise and vibration. The dis-advantage is the high initial cost. 3.
Choice of appropriate Ballastless Track for Bangalore Metro
The tracks for Bangalore Metro are mostly laid on viaducts and Tunnels, and the alignment passes through the busiest part of the city. Once commissioned, train services will operate on the system for about 19 hours, leaving about 5 hours in the night for maintenance. For these reasons, the track designed should be of minimum weight, have long life with little or no maintenance and should be environment friendly. The track base needs to be integrated with the civil structure to provide the longitudinal and lateral resistance. The elastic fastening system should provide the necessary support, vertical elastic stiffness and noise/vibration abatement. Considering the above requirements, Ballastless track with elastic fastening system using discrete rail supports (sleeper principle) has been chosen as the ideal system for Bangalore Metro. The track is supported on monolithic in-situ slabs or pedestals on civil structures such as viaducts/bridges and tunnels. Plinth design has been adopted for Viaducts and At-grade track and slab design for Tunnels and Turnouts. Both these designs are referred to as ‘track slab’. The ‘track slab’ has been designed to resist the track forces and transmit them to the supporting structure. The design is construction friendly and easy to maintain. 322
For Bangalore Metro, Fastening system-336 has been adopted for fixing rails to ‘track slab’. The ‘track slab’ is anchored to the supporting structure through shear anchors.’Top-down construction methodology’ has been adopted for execution of Track work.
4.
Ballastless Track on viaducts.
4.1. Typical designs. There are four designs for Ballastless Track on viaducts, namely • Ballastless Track on Tangent Track • Ballastless Track on curves of radius flatter than 190m radius • Ballastless Track on curves 190m radius and sharper, provided with check rails • Ballastless Track for Turnouts. In all the four designs, the plinths are cast in sections of lengths varying from 3.5m to 6m with 200mm gap in between for drainage, ease of execution and effective stray current collection. 4.1.1. Ballastless Track on Tangent Track The track is supported on a concrete pedestal, and the pedestal is anchored to the viaduct slab using shear anchors projecting from the top slab of the viaduct. Derailment up-stands are provided on the inside of track providing a clearance of 250±40mm between the rail and the up-stand. As per guide lines issued by the Railway Board, the up-stand top should not be lower than 25mm below the rail top. The up-stand top has been kept 10mm above rail level to provide adequate wheel back to upstand contact area for trapping a derailed wheel, at the same time keeping the up-stand top outside the structural envelope of the coach. 323
A sketch of the pedestal arrangement is at Fig.1
Figure: 1
4.1.2. Ballastless Track on curves flatter than 190m radius. This design is similar to that of Tangent track, except that the track supporting pedestal is canted to provide the designed cant for track. The top of up-stand should be designed such that it provides resistance to the derailed wheel of a coach traversing a canted track while not infringing the structure gauge. It is to be noted that, to achieve this objective, the top of up-stand is kept above outer rail and below inner rail by 10-15mm. The effect of cant on up-stand height is shown in Fig.2
Figure: 2 324
A sketch showing the pedestal arrangement is at Fig.3
Figure: 3
4.1.3. Ballastless Track on curves of radius 190m and sharper, provided with check rails. This design is identical to that of curved track at para 4.1.2 above except that the pedestal should provide additional width for housing the check rail assembly. Check rails using C1-33 rails, mounted independent of running rail, have been provided. The check rail clearance has been kept at 56mm. To facilitate provision of check rails, up-stand has been shifted to out-side of track. A sketch showing the pedestal arrangement is at Fig.4.
Figure: 4 325
4.1.4. Ballastless Track for Turn outs. Due to the Turn out track taking off from main line in the Turn out assembly, pedestal arrangement is not suitable for Turn outs. Turn outs are laid on slab base. The rail supports are on raised pedestals. The Turnout slab is divided into segments to facilitate drainage and ease of concreting. The up-stands are provided outside the track. The Turnout supports are designed radial to the turn out curve(fan shaped). A fan shaped lay out does not go well with the simply supported spans, as the rail supports often foul with the girder expansion joints. For this reason, when Turn outs are laid on viaducts, the superstructure of the spans supporting the Turnout/cross over is made continuous. A sketch showing the slab arrangement in plan for cross over is at Fig.5.
Figure: 5 326
A sketch showing the view in cross section is at Fig.6
Figure: 6 5.
Ballastless Track in circular Tunnels.
The lay-out of Track in circular tunnels is simplified by providing a filler raft using concrete which provides a flat surface for a RCC slab to support the track. Anchorage of ‘track slab’ to the filler raft is provided by 4 numbers, 25mm diameter Anchor bolts in plastic dowels at 700mm centers installed in the first 100 metre from tunnel portal to the inside of the tunnel. The design should take into account the problems of drainage and passage of cables and other accessories. A sketch showing the slab arrangement in Tunnel for tangent track is at Fig.7.
Figure: 7 327
A sketch showing the slab arrangement in Tunnel for curved track is at Fig. 8
Figure: 8
6.
Ballastless Track in Rectangular boxes.
Here, the ‘track slab’ is laid directly on the bottom slab of the box . The slab is interconnected to the box using shear reinforcement left out while concreting 150mm base concrete over the bottom slab of the rectangular box. A sketch showing the track arrangement in box Tunnel is at Fig.9.
Figure: 9 328
7.
Ballastless Track on At- Grade sections.
Ballastless track on earth sub-grade has to address the problem of differential settlement of sub-grade. A stiffness of compacted base layer of more than 80N/mm2 and a compaction factor of 0.97 has been stipulated. Besides soil improvement, risk of differential settlement is decreased by increasing the flexural stiffness of the super structure by providing a concrete slab. A sketch showing the track arrangement in At-grade lengths is at Fig.10
Figure: 10
8.
Transition Tracks. Special construction is required •
Between ballasted track At-grade and ballastless track At-grade
•
Between ballastless track At-Grade and ballastless track on viaduct
•
Between ballastless track in Tunnel and ballastless track At-grade. 329
9.
Third rail installation.
The plinth design provides for specific cast-in-situ pedestals to support the brackets for third rail at spacings designed by the Traction contractor. The spacing varies from 5m in tangent track to 3.5m in the sharpest curve of 120m radius. The brackets are fixed by installing two numbers, 31mm dia plastic inserts, with an internal diameter of 25mm, into which M24 screw spikes are inserted. A sketch showing the bracket support is at Fig. 10 10. Fastening System 10.1.Functions The fastening system is, by far, the most important component of the Ballastless track. The fastenings shall have a proven record of minimum five years satisfactory performance, and should be compatible with the traction and signalling requirements. The Fastening system has the following functions to perform. • Fixes the rails in the correct position, to correct inclination, gauge and alignment • Controls the longitudinal and lateral displacement of rails within the specified range • Provides elasticity to the track in the vertical and lateral directions - an important function performed by ballast in ballasted track • Prevents the rails from overturning • Transmits the forces on to the track support • Resists the longitudinal and transverse displacement of track structure • Permits easy installation • Permits vertical adjustment during service life up to 12mm • Attenuates the noise and vibration. 330
10.2.Performance requirements Performance requirements of Fastening system for Ballastless track has been laid down by Railway Board vide letter No.2009/Proj/MAS/9/2 dated 21-05-2010. The salient features of the Performance criteria are summarised below. Sl. No 1 2
3 4 5
Technical parameter Longitudinal restraint Static Vertical stiffness of the Fastening system(in the secant range 5-80kN) Dynamic/static stiffness ratio Clamping force Electrical resistance
Test Method EN-13146-1 EN-13146-4
EN 13481-5 EN-13146-7 EN-13146-5
6
Effect of severe environmental conditions
EN-13146-6
7
Effect of repeated loading (for test load & fastening position, refer EN-13481-6) (a) On vertical stiffness
EN-13146-4
(b) On Longitudinal restraint
EN-13146-1
(c) On clamping force
EN-13146-7
EN-13146-4
331
Acceptance criteria 7kN(min) 35kN/mm(max) No sliding, yield or cracking is allowed for the fastener parts 1.4(max) 18kN(min) 5kΩ(min). Higher value if required for track circuit As per EN-13146-6 The fastening system shall be capable of being dismantled, without failure of any component, using manual tools after exposure to salt spray test. No wear or deformation
No sign of bond failure/fracture/slippage. Variation less than 25% of initial value Variation less than 20% of initial value Except the rail and fastener, no sliding, yield or cracking is allowed for fastener parts. Longitudinal load/deformation curve shall fall in the envelope of upper and lower limit Variation less than 20% of initial value
10.3.Test Requirements for Fastening components. The design of the fastening system is left to the individual designer who develops the system. Accordingly, the components of the fastening system can vary . The supplier of the fastening system should ensure that the system, when assembled and tested, meets the criteria laid down for the project. He should also lay down the specifications and test plan for the individual components so that the required quality can be ensured consistently. Of the various components, quality and performance of three components need special monitoring. These are, (i) Elastic pad, (ii) Tension clamp, and (iii) Rail pad. The Elastic pad should be tested for Static Elasticity, Dynamic Elasticity and Volume resistivity apart from the property of the material of the pad. The dynamic/static stiffness ratio between 18 and 68kN should not exceed 1.40. The Tension clamp should be essentially tested for hardness, fatigue resistance and corrosion protection. Rail pad should be tested for Shore-D-Hardness, Melt flow rate, density and volume resistivity. 10.4.Fastening system adopted in Bangalore Metro Fastening system-336 with Skl-12 Tension clamp supplied by M/s Vossloh, Germany has been used in Bangalore Metro. The base plate system uses an M27x285 mm cast- in anchor stud assembly. Two such bolts are used on curves flatter than 700m radius, 4 bolts on curves sharper than 400m and 3 bolts for curves <700m and ≥400m. The fastening system is capable of lateral adjustment of ±4mm using eccentric insulating bush and vertical adjustment of +20mm using a combination of height adjustment plates beneath the base plate. 332
The fasteners are spaced at 700mm on tangent track and on curves of radius 400m and flatter. The spacing is reduced to 650mm on curves sharper than 400m radius. This system has a proven record in Indian conditions of over 10 years on the BG & SG systems of DMRC, Delhi. Its performance in Reach-1 of Bangalore Metro for the last 14 months has been quite satisfactory. A sketch showing the Fastening assembly is at Fig. 11
Figure: 11
11. Broad parameters adopted for design of Ballastless Track for Bangalore Metro. 11.1.Track System definition The track work consists of UIC 60 HH rails of 1080 Grade with 1:20 inclination laid to standard gauge, supported on Fastening system-336 fixed to on reinforced concrete plinths at 650-700mm centres. The plinths are directly cast on the viaduct decks and anchored with anchor bars. 333
11.2.Design Loads The system is designed for a maximum speed of 90 kmph. Axle configuration of standard coaching stock is at Fig.12.
Figure: 12
The loads taken for design of the plinth are as under. (i)
Axle Load-15 Tonnes
(ii) Impact factor Impact Factor ᶲ=1±0.3 (iii) Braking and Traction Braking and Traction force is 20% of vertical axle load (iv) Centrifugal force. This has been worked out for 90 kmph for a curvature on which 90 kmph speed is permissible. Maximum centrifugal force for 90kmph for R=425m, is 22.1kN (v) Hunting Force Hunting Force is taken as HF=0.08Fa where Fa is the load of the leading axle. (vi) Guide Force Guide force is taken as, GF= 10+Fa/3=59kN, and is applied for curves smaller in radius than 500m radius. For straights and 334
curves >500m, the transverse force from rail wheel contact is taken as Y=HF+CF+WF, Acting exclusively on the outer rail and leading axle. (vii) Wind Force Wind force is worked out as 13.8kN/axle for a maximum allowable gust speed for operation of v=35m/sec (viii) Track work-structure Interaction Force A study of the Track-Viaduct structure interaction was conducted to know the impact of deformation of the viaduct structure on track. It was concluded from the results of study that additional stresses from viaduct girder volume change, live load, braking, traction and girder end rotation are far below the limit specified in UIC 774-3, and fracture gap of a broken rail was only a maximum of 31mm (< 50mm). Thus, no SEJ is proposed in the system, track being welded end to end. Creep resistance of fastening system ≤( 10.5kN/fastening ) limits the maximum force exerted by the track work- structure interaction. For a fastening spacing of 0.7m, Force/m=10.5/0.7=15kN/m (ix) Force due to temperature, shrinkage and creep of girder As a result of these forces, longitudinal displacement difference occurs between girder and track. A temperature difference of 10K is adopted. (x) Derailment Impact A force of 100kN is taken as accidental load acting on top of derailment up-stand horizontally and perpendicular to the track axis.
335
(xi) Vertical load. The rail offers stiffness and the fastening system offers flexibility resulting in distribution of wheel forces along the track.Taking the track system as a beam on elastic foundation and applying Zimmermann equation, a load distribution factor of 0.4 for the directly loaded fastener and 0.3 for the adjacent fastener has been taken. For calculation the computer code STRAND 7 is used. 11.3.Plinth lengths The lengths of plinth segments are designed from the following considerations. (i)
Plinth segments should over lap the girder segment joints by a minimum of 300mm with at least one shear anchor placed in the overlap. (ii) The length should be so designed that the number of rail base plates at the designated spacings is the minimum. (iii) The third rail brackets are away from the plinth segment ends. A typical plinth arrangement for 25m span for tangent track is at Fig.13.
Figure: 13 336
12. Track tolerances after installation and during service The following Track tolerances should be achieved on installation and during service. Sl.No 1 2 3 4 5 6
Parameter Gauge Cross level-tangent track Cant-curved track Vertical alignment over a 20m chord Lateral alignment over 20m chord Curves-variation over theoretical versine over 20m chord
Installation +2,-1mm ±1.5mm
Maintenance +4,-2mm ±5mm
±1.5mm ±3mm
±3mm ±6mm
±2mm
±6mm
±2mm
±5mm
13. Noise and vibration Attenuation Measures Ground-borne noise and vibration associated with transit operations were studied for their impact on the stability of structures in the vicinity of the alignment in general, and on the functioning of sensitive installations like hospitals and communication centers in particular. The study showed that the impact was significant from ground-borne noise and vibration on structures in the vicinity of underground transit-way. All existing structures falling within 15m beyond the tunnel/cut and cover box have been considered for deciding the length of track for which floating slab is to be provided. Noise/vibration attenuation measures have been proposed in those stretches by provision of 25mm elastic pad below the track slab. No shear connectors will be provided in the lengths identified for provision of floating slab, even when it falls within 100m of tunnel portals. In such lengths, concrete shear blocks will be provided at 15m centres in lieu of shear connectors. 337
Sketch showing the arrangement for provision of elastic pads is at Fig. 14
Figure: 14
A sketch showing the shear block arrangement in ramp portion is at Fig.15.
Figure: 15 338
14.
Design Inter-face with Signalling System contractor.
Impedance bonds are required to be provided by the Signalling system contractor for providing return current to Traction sub-stations. Stationary train indication beacons are also to be provided by them for signalling requirements at stations. The track plinth dimensions should be designed to accommodate these requirements. In the design of track sub-structure for the switch portion of Turn outs, the signalling requirements for switch operation and interlocking should be taken into consideration. The Track drawing should be cleared by the Signalling system contractor. 15. Design Interface with Traction System contractor 15.1
Stray current
Stray current is that part of the return current which is not using the rail as the return current path. Stray current can cause corrosion of track components and corrosion of all other steel components coming in the way of its strayed path. Provision for protection against stray current involves two stages. (i)
The insulation of running rails against earth and structure earth to prevent the return current entering the ‘track slab’. This is taken care of by the insulating system of the Fastening assembly comprising rail pad, Elastic pad and Insulating bush.
(ii) Collection of stray current, if any, from the ‘track slab’ through longitudinal earthing bars placed below the rails in the ‘track slab’. The earthing bars are longitudinally inter connected and cross connected at regular intervals for collection of stray current and earthing.
339
A schematic diagram showing the stray current disposal arrangement is at Fig.16
Figure: 16
15.1.1 Results of Field measurement for Electrical Resistance of Plinth Track on viaduct. The track already commissioned in Reach-1 and under construction in Reach-3 were tested for Electrical Resistance on 27.02.2012 & 28.02.2012 and the results are as under. 1. Rail resistance was recorded as 35m Ω/km in Down track and 36mΩ/km in Up track .These values are considered very good for 60E1 rail section. 2. Rail to structure resistance measured in Reach-3 showed that the track had 8 times the minimum stipulated resistance. 3. Conductance S/km was within permissible maximum of 0.05. 340
15.2
Placement of supports for third rail brackets
15.2.1 Third rail supports for Normal track. The Third rails are delivered in 15m lengths. The third rail allows a spacing between two consecutive support brackets of 5.20m. A bracket spacing of 5m has been adopted as maximum for tangent tracks. Accordingly, in the depots provided with concrete sleepers at 700mm spacing, every 7th sleeper should be designed as longer sleepers to mount the brackets. The spacing of bracket supports gets progressively reduced as curvature increased, the maximum spacing permitted in the sharpest curve (120m on main line and 100m in depots) being 3.7m. Supports are also required for splice joints (to connect two conductor rails), expansion joints, mid-point anchor supports (between two expansion joints) and ramp supports. While planning the plinths for ballastless track, the important requirement is that the gap between plinths for rails should not come in the way of the bracket supports. Plinth lengths for track should be decided in consultation with Traction contractor. 15.2.2 Third rail supports for Turn outs In the case of ballasted track, longer length special sleepers are required to be provided with dowels for fixing the brackets, wherever Third rail supports are required. The extended length is to be provided on the straight side or Turnout side depending on which side the support is located. For ballastless track, Third rail supports are placed on derailment up-stands. 16 Certain guide lines in the design and execution of Ballastless Track. (a) Unlike ballasted track, ballastless track, once installed, is very difficult to correct. The design and its execution has to be done with utmost precision and care.
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(b) Since the elevated tracks have to be laid in standard width decks, the tracks are laid as concentric curves. Thus, the radius of outer track will be more than that of inner track by the distance between the two tracks. (c) The track centres depend on the track radius. Varying the track centres to suit the curve radius will complicate the lay-out in elevated track and the viaduct design and construction. It is, therefore, advisable to keep the track centres corresponding to the sharpest curvature throughout the length of the elevated track. In Bangalore Metro, track centres throughout Viaduct and At-grade alignments has been kept 4.20m (d) The height of up-stand on curved alignment should be regulated to suit the tilted kinematic envelope. (e) The increased clearance requirements on curves should be applied for 20m beyond the section to which it pertains. This is to allow for end throw/mid throw and cant effect as the coach enters/ leaves the curve.
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LAYING OF BALLASTLESS TRACK SYSTEM IN PIRPANJAL TUNNEL -Vinod Kumar, Dy.Chief Eng./C/Northern Railway, Banihal __________________________________________________________________________
Synopsis: Pir Panjal Tunnel also known as Tunnel T-80 is being constructed by Northern Railway in Udhampur-Baramullah-Srinagar-Rail Link Project. This tunnel is 11.215 Km (including Cut & Cover portion of 255 meters) long and is India’s longest transportation tunnel. This tunnel has been provided with 3.0 meter wide road along with track to be used for maintenance and rescue operations. In order to have maintenance free track inside this long tunnel, it was decided to provide ballastless track inside this tunnel since conventional ballasted track requires frequent track maintenance to maintain the track geometry. A number of ballastless track technologies exist now a day. Rheda-2000 ballastless track system has been adopted in Pir Panjal tunnel. The prerequisite of providing this ballastless track system is high degree of precision and quality during construction stage as it is very difficult to alter the track parameters or repair it later on. This paper deals with the various steps and methods which have been followed for construction of Rheda-2000 Ballastless track system in Pir Panjal Tunnel. 1.
INTRODUCTION
Rheda – 2000 ballastless system using RHEDA® - 2000 Semi Precast Bi-Block sleepers of M-55 Grade and Vossloh 300-1 U Fastenings has been used to provide ballastless track in tunnel T-80. This Ballastless track system is relatively maintenance free as compared to conventional ballasted track. In this system the Rheda2000 Semi Pre-cast Bi-Block sleepers are embedded in the RCC concrete bed and the rails are held on sleepers with Vossloh 300-1 U fastenings. The sleepers are produced in sleeper factory. The 343
advantages of using Rheda-2000 Ballastless track system include long life cycles, high speeds, ride comfort and great load-carrying capability. Practically maintenance free, ballastless track systems ensure 100% availability over many years. In many cases, a maintenance-free track system is indeed the more cost-effective solution over the long run. 2.
STRUCTURE OF BALLASTLESS TRACK SYSTEM
The structure of the ballastless track system adopted in Tunnel T-80 consists of:
2.1
(a) Rails
(b)
Fittings
(b) Sleepers
(d)
Insitu Concrete
RAILS
The rails being used in Pir Panjal Tunnel are 60 KG HH rails. These rails have been imported from Austria. 2.2
FITTINGS
Vossloh slab track system 300-1 U with tension clamp Skl 15 (Photos 1 & 2) is being employed as the fittings for ballast less track in tunnel T-80. The fastenings are composed of the following parts per sleeper: (a) Elastic Pad ZWP 104 NT
2 Nos.
(b) Steel Base Plate Grp 21
2 Nos.
(c) Rail pad ZW 692
2 Nos.
(d) Angle guide plate Wfp 15 U
4 Nos.
(e) Sleeper Screw Ss 36
4 Nos.
(f)
4 Nos.
Plastic Dowels Sdu 26
(g) Tension Clamps Skl 15
4 Nos.
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Photo 1: Vossoloh fittings
Photo 2: Assembled fittings
Vossloh fastening system provided support, guidance, resilience and insulation between rail and sleepers. These are simple to install, screwed type and can be visually inspected for any defect. 2.2.1
Elastic Pad ZWP 104 NT (Photo 3)
The elastic pads are provided on rail seat of the sleepers and substitutes for the elasticity of ballast bed. These pads are manufactured from PU, Rubber or EDPM. The physical properties for elastic pad are as follows: • •
Static Elasticity Dynamic Elasticity
•
Volume Resistivity
2.2.2
22.5 KN/mm at roo temperature. < 1.4 under static load in 5 Hz frequency in room temperature >108 Ohm cm
Steel Base Plate Grp 21 (Photo 4)
Hot rolled wide steel plates are provided between rail pad and elastic pad to ensure proper distribution of load on elastic pads.
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The physical properties for base plate are as follows:
Tensile Strength Elongation at break Yield Point
Min 410 MPa Min 20 % Min 275 Mpa
Photo 3: Elastic Pad 2.2.3
Photo 4: Steel Base Plate
Rail Pad ZW 692 (Photo 5)
Rail pads are provided to support rails and are placed below rails in between the angle guide plates. These pads are manufactured from Ethylen-Vinylacetat –Copolymerisat (EVA) and are stabilized against UV damage. The physical properties of rail pad are as follows: 2.2.4
Hardness Melt Flow Rate Density Volume Resistivity
32-47 Shore 2.16/10 min <= 0.962 g/cm3 >108 Ohm cm
Angle Guide Plate Wfp 15 U (Photo 6)
Angle guide plates are manufactured from Polyamide with 30 % glass fiber reinforcement provided to laterally hold the rubber pad below rails at the same position. Two numbers of angle guide plates are provided per block of sleeper. 346
The physical properties of angle guide plate are as follows:
1.30-1.45 g/cm3 1%-2.5 % >108 Ohm cm
Density Moisture Content Volume Resistivity
Photo 5: Rail Pad 2.2.5
Photo 6: Angle Guide Plate
Sleeper Screw Ss 36 (Photo 7)
The sleeper screw is manufactured in accordance with DIN EN ISO 898-1. The physical properties are as follows:
Tensile Strength Elongation at break Yield Point
Min 500 MPa Min 20 % Min 300 Mpa
These screws are hot galvanized to ensure protection from corrosion. 2.2.6
Plastic Dowels Sdu 26
The plastic dowels are embedded in sleepers during casting of sleepers. These dowels are manufactured from polyamide and are resistant to UV damage. The physical properties of the dowels are as follows.
1120-1150 g/cm3 >108 Ohm cm
Density Volume Resistivity 347
2.2.7
Tension Clamp SKL 15 (Photo 8)
Tension clamps provided over the guide plate and tightened by bolts provides nominal toe load of 9 KN per clamp i.e. minimum toe load of 18 KN per fastening point. The rails are permanently tightened by spring actuation as a result of long elastic spring. Any tilting and lifting of rails are also prevented by the tension clamp as the middle bend of clam absorbs the same. The physical properties of Tension clamp are as follows:
Hardness Fatigue resistance
400-460 HV 5 million cycles of amplitude 2.6 mm
Photo 7: Sleeper screw
2.3
Photo 8: Tension Clamp
SLEEPERS
The sleepers for this Ballastless System are Semi Pre-cast Bi-Block sleepers which consist of two blocks (Photo 9) which are linked with each other with two lattice girders. These lattice girders prevent relative movement of independent blocks and simultaneously act as reinforcement for the twin blocks. Two plastic ferrules and bursting coils per block are casted in the blocks which hold Vossloh 300-1 U fittings. These sleepers were produced at Manwal Sleeper factory which was set up by M/s Patil Rail Infrastructure Limited. The brief procedure for production of sleepers is as under: 348
The approved moulds (Photo 10) are cleaned with the help of wire brush and oiled followed by placement of reinforcement lattice girders, plastic ferrules and bursting coils. The concrete is produced in the batching plant and manually filled in the moulds. Materials for production of concrete are tested in the prescribed frequency in accordance with the relevant IS codes. After filling the moulds with concrete, compaction of concrete is done by vibrating the moulds by high frequency vibrators (9000 RPM) attached to the vibrating table. The moulds are then shifted to the steam curing chambers. Steam curing of moulds is done so as to achieve minimum demoulding characteristic compressive strength of 40 MPa in one day. After the mould has been placed in the steam chamber, precuring for 2 Hrs at 30oC is done followed by 2 Hrs of rising period at the rate of 16oC per hour and then the standing period of 5 Hrs at the maximum temperature of 60 o C. Temperature of chamber is reduced to 30 o C in next 2.5 Hrs. After steam curing, Sleepers are demoulded and transferred to water curing tanks. Submerged curing of sleepers is done for 15 days so as to achieve characteristic compressive strength of 55 MPa.
Photo 9: Rheda 2000 Semi Precast Bi block Sleeper 349
Photo 10: Moulds with lattice girders and dowels 2.3.1
Quality Assurance in Production of Sleepers
The production of sleepers has been done as per the approved Quality Assurance Plan which enumerates controlling of processes through Receiving Goods Inspection and in Process inspection. •
Receiving Good Inspection
All the raw materials i.e. Cement, Aggregates, Mixing water, Plastic Screw dowels ,Track Fastening materials and Reinforcement etc. are inspected in regular intervals as specified in relevant IS and DIN codes. •
In-process Inspection
In process inspection of all the processes involved in casting of sleepers has been defined as per relevant codes and frequency. Such inspections ensure standardization of production process and minimize deviation from the approved quality. In the in process inspection after curing of sleepers and before dispatch, all the sleepers are inspected for the following: 350
•
Surface Condition
Sleepers are visually inspected for any defects in the surface condition of the sleepers as per the stipulations of European Standard DIN EN 13230-1 and only those sleepers which are found free from any surface defects like blow holes, honeycombing and cracks are then further inspected for cracks in rail foot bead. •
Cracks in Rail seat
Cracks in rail seat which are not visible are detected with the help of acetone. Those sleepers having cracks on rail seat are rejected and rests are checked for the dimensions. •
Dimensional Inspection of Sleepers
Sleepers found free from all the surface defects are inspected for dimensional tolerances. Standardized precision gauges templates have been made for inspection of sleeper dimensions. Following tolerances has been specified: S.No.
Description
Dimension in mm
D.1
Outer to outer length of reinforcement
2702+-5
D.2
Outer to outer length of Sleeper
2473+-10
D.3
C/C distance of rail seat
1765+-1.5
D.4
End to End spacing of rails seat measured 28 mm above rail seat
D.5
Gap between blocks
645+-6
D.6
Length of Blocks
914+-8
D.7
Length of Rail Seat measured 28 mm above rail seat
D.8
Slope of Rail Seat
D.9
Concrete Cover to Lattice top from top of the block.
2139.6+-1.5
375.7+-1 1 in 20 +-0.5
351
70+-3
D.10
Height of Concrete Block
D.11
Width at Bottom of Concrete Block
D.12
Cross Twist between blocks
13
2.4
142+5/-3 286+-5 <0.7 mm 1 mm on base of 150 mm scale
Flatness of Rail seat
INSITU CONCRETE
Insitu concrete in Ballastless track in Tunnel T-80 is being done in three stages as under: (a) Plain Cement Concrete (PCC). (b) Track Concrete Layer (TCL). (c) Derailing Block (DB). 2.4.1
PLAIN CEMENT CONCRETE (PCC)
PCC is placed over the drainage layer (tunnel without invert) or permanent invert concrete (tunnel with invert) at 764 mm below rail level up to 473 mm below rail level. This 291 mm thick M-20 layer acts as a base concrete layer. The PCC is casted in segments of 50 m length. 2.4.2
TRACK CONCRETE LAYER (TCL)
The ballast-less track in Tunnel T-80 consists of semi pre-cast biblock RCC Rheda-2000 sleepers manufactured using M-55 Grade Concrete with the lower part of lattice girders projecting outside the concrete body of the sleeper. For rail fixing, dowels which are part of Vossloh fittings are embedded while casting the sleepers. These sleepers are embedded in RCC layer of 243 mm thickness. This layer is called Track Concrete Layer (TCL) and is of M-35 grade concrete. The TCL consist of two layers of reinforcement with both bottom and top layer composing of rebars of 16 mm ø in longitudinal direction and transverse direction. The track concrete layer is placed 352
over 291 mm thick M 20 grade PCC base layer concrete. The procedure for casting of TCL is explained in the following paragraphs. Placing of Sleepers The precise track centre at every 5.4 m on straight track is marked by the survey team using Total Station on the already laid PCC as explained in para 3.0 below. The Rheda-2000 sleepers are shifted inside the tunnel using pick and carry crane and Tractor – Trolley. The sleepers are then placed at 600mm spacing c/c along the centre line of the straight track over the PCC. Fixing of Rails The elastic pad, steel base plate, rail pad, inner angle guide plate and inner sleeper screw are first fixed on to the sleepers and then the rails are shifted over the sleepers by lifting the rails with help of track jack and rail tongues, manually. After that the outer angle guide plates and sleeper screws are fixed. The sleeper screws are tightened with the help of torque wrench and initial torque of 120-150 Nm is applied on them after insertion of tension clamps on the rail foot and maintaining the gauge with due consideration to the track centre line. The use of torque wrench ensures the even bracing of rails. The outer screws are tightened first followed by the inner one. Fixing line and level The track is then lifted with the help of spindles (Photo 11) fixed at very third sleeper (1.8m) to the designed level which is pre-marked on tunnel wall as a continue line by survey team using Digital Leveling Instrument. The spindle brackets are provided in the middle of sleeper spacing with the spindle on the inner side of the rail. At the location of rail joint, one sleeper at the most remains unsupported i.e., the normal distance of providing spindles at every third sleepers is interrupted. The track is leveled and adjusted to match the marked track centre line and designed levels. The alignment is maintained by using turn buckles (Photo 12) bearing against the tunnel wall on one 353
side and road concrete on other side. The sleeper distance and squareness is checked and corrections made as required so that track parameters are within the tolerances.
Photo 11: Rail supported on spindle
Photo 12: Lateral support by turn buckles
354
Placing and binding reinforcement After the track has been supported on spindles and aligned with the help of turn buckles along the required centre line, both longitudinal & transverse reinforcement is placed (Photo 13) starting from bottom layer to top layer and tied with the help of binding wire. The top layer reinforcement is tied with the lattice provided in the bi-block sleepers so as to avoid any displacement of sleeper during concreting. The minimum concrete cover of 30 mm as specified in drawings is being ensured for concreting.
Photo 13: Placing and binding of reinforcement in TCL
Concreting Before commencement of concreting all the track parameters are measured and recorded and it is ensured that these are within permissible track tolerances. In order to protect fittings and rails from splashing of concrete during casting of TCL, these are covered with sheet covers. Concrete of M-35 Grade manufactured in automatic batching plants and transported in transit mixers is used in TCL. The entire thickness of TCL is filled in one layer with bottom of TCL at 473 mm and top at 230 mm from rail top. The compaction of concrete is 355
ensured by needle vibrators. The central portion of TCL is made rough to receive concrete for Derailment Block. After the completion of concrete for TCL, the fittings and rail foot are cleaned from any residual concrete. When the concrete becomes sufficient hard, the rails are made free by loosening the tension clamps by unscrewing the sleeper screws so that the shrinkage stresses of the concrete are not locked up by the fixed rails. Generally, the clamps are being released when the concrete becomes sufficient hard by about 6 hrs. The spindles are removed after 12 hrs of concreting and the holes created by spindles are filled by non shrinkable cement grout. 2.4.3
DERAILMENT BLOCK
The derailment block is laid with same grade of the concrete as in TCL i.e. M-35. Special fabricated shuttering plates (Photo 14) are used for casting of derailment block. The derailment block performs the functions of guard rail on normal track. The width of derailing block in the central portion is 1173 mm with height of 230mm. The clearance of 250mm of derailment block from gauge face of the rail is maintained. Also clearance of 180mm is provided on non gauge side of the rail. The clearances are kept such that the sleeper fittings could be removed easily on one hand and road vehicle could move over the track on other hand in case of emergency.
Photo 14: Shuttering Plates for Derailment Block 356
Photo 15: Derailment block shuttering fixation in progress.
Photo 16: Finished Ballastless Track System inside Pir Panjal Tunnel 357
3.
SURVEYING
Surveying is done in following two parts: (a) Fixing the centre line of track i.e. Northing & Easting coordinates. (b) Fixing the rail level i.e. elevation.
3.1
FIXATION OF CENTRE LINE
This is done with the help of total station (Photo 17). Temporary Bench Marks are provided at every 50 m by fixing the Bireflex targets (Photo 19) or mini prism (Photo 20) arrangements. Small MS plates of size 25mm x 12mm x2mm (Photo 21) are welded with 8mm dia bolts. Holes of 8mm dia are drilled in the PCC at approximate centre of the track and the plates are fixed in these holes (Photo 22). These MS plates are fixed at distance of 5.4 meter i.e. every 9th sleeper. Two sleepers are placed over the two adjacent reference plates matching the centre of sleeper over the punch mark (Photo 18) on reference plates. A nylon cord is stretched at the right hand outer edge of these two sleepers and all the sleepers in between these two sleepers are placed in alignment by touching the right outer edge of the sleeper with the nylon cord. When the track is lifted and rails are placed over the spindles after fixing the rail level the centre line of the track may disturb. For adjusting the centre line after placing the rails on spindles, half gauge (Photo 23) is used. One rail is adjusted with respect to centre line by using the turn buckles and other rail gets adjusted automatically due to fixed gauge of sleepers. Turn buckles are provided at every third sleeper and rests on the web of the rail. A wooden block is placed between turnbuckle and rail web to avoid damage to the rail.
358
Photo 17: Alignment fixation by Total Station
Photo 18: Centre line marking on reference plate with mini prism 359
Photo 19: Mini Prism
Photo 20: Bireflex target
Photo 21: Reference plate
Photo 22: Reference plate with punch mark
Photo 23: Half Gauge for adjusting alignment 360
3.2
FIXATION OF RAIL LEVEL
Rail levels are fixed with the help of digital leveling instrument (Photo 26) and bar coded staff (Photo 27). Building monitoring points (Photo 24 & 25) are fixed inside the tunnel lining at every 50 meter interval to be used as Temporary Bench Marks. The designed levels of the track are transferred on right hand rail by Spindle jacks by lifting/lowering these. The levels of left rail are corrected by using the cross level and gauge.
Photo 24: Building Monitoring Point
Photo 25: BMP fixed inside lining
Photo 26: Digital Leveling instrument
Photo 27: Bar Coded Staff
After completing the reinforcement work, the track parameters are again checked & corrected. Gauge & cross levels are checked with the help of Gauge Cum Level and alignment of track is checked by taking versines at every 10 m on 20 m chord. The track parameters in the BLT are maintained to the following tolerances. 361
NEW BALLASTED TRACK S.No.
TRACK PARAMETER
(PARA316 OF IRPWM) TOLERANCES
1
Gauge
2
Sleeper Spacing
3
Square-ness of Sleepers
4
Cross Level
20mm (w.r.t. theoretical spacing)
+/- 3mm
(On St. Track) 5mm variation over theoretical versines Alignment
TOLERANCES
MEASUREMENT CRITERIA
+/- 1mm (Over prescribed gauge)
On Each Sleeper
1 mm (Sleeper to Sleeper variation)
On Each Sleeper
+/- 5mm
Each Spacing
+/- 2mm
Each Sleeper
Every 4th Sleeper
+/- 1mm
Every 2M
On 10M Chord
+/- 2mm
With 20M Chord half overlapping
2mm(Sleeper to Sleeper variation)
+/- 2mm
5
MEASUREMENT CRITERIA
(On Curves of R>600M) 10mm variation over theoretical versines (On Curves of R<600M)
BALLASTLESS TRACK
(Each Spacing)
Every 10M using 20M Chord
Every 10M using 20M Chord
362
+/- 2mm (Versine variation over theoretical versines
With 20M Chord
With 20M Chord
6
Longitudinal Level
50mm (With reference to approved longitudinal sections)
7
Square-ness of F/P Joints
+/- 10mm
Twist
2mm/Mtr on St & Curved Track and 1mm/Mtr on transitioned portion.
8
+/- 4mm
Longitudinal level profile with Station at every 20M in relation to designed layout.
Every Joint
+/- 5mm
Every Joint
(Para 607 of IRPWM)
2mm on 3.60M base.
363
CONSTRUCTION OF WASHABLE APRON BY RHEDA 2000 TECHNOLOGY - S.S. Khongrymmai, Sr.DEN/I/APDJ, N.F.Rly - B. Chakraborty, ADEN/HQ/APDJ, N.F.Rly
Synopsis: One of the ugly sights of Indian Railways is the dirty and stinking Railway Stations. Filthy atmosphere and toilet drops at terminal stations cause air pollution and health hazard for the traveling passengers. The dirty Railway Station is always a deterring factor for a traveler who is going to make his maiden trip by railway. Effort to improve the cleanliness at major railway stations has been initiated long back but without much success. One of the main reasons is cleaning of toilet wastes. This aspect has been catered by means of construction of conventional washable apron in a large no. of major stations over Indian Railways. However, these conventional washable aprons did not prove good enough due to the inherent defect in its design. The bituminous concrete around the PSC sleepers generally come out within 1 to 5 years causing defects in the track geometry, damage to sleepers and cleaning problem of toilet wastes. Thus the total investment on this aspect becomes completely superfluous and the thought of repairing and cleaning becomes a nightmare for the railways. This paper discusses on a Washable Apron with improved technology of RHEDA2000 giving a special emphasis on the apron developed at New Alipurduar station Line No.3. Introduction: The conventional Washable Apron conforming to RDSO Drawing No. RDSO/T4781(R) was constructed at New Alipurduar Station in 2007-08, New Coochbehar Line No.4 during 2009-10 and 365
New Coochbehar Line No.1 during 2010-11. The washable apron of New Alipurduar is now damaged due to coming out of the bituminous layer. The track is supported at number of stretches with the help of wooden pieces. After one year of construction of Washable Apron at Line No.4 at New Coochbehar, the bituminous layer came out and the washable apron was modified by removing the bituminous layer. Similar is the case of washable apron at Line No.1 at New Coochbehar. Further it is observed that other stations of Indian Railway are having the same problem with the conventional washable apron. Thus the conventional washable apron is practically not economical, rather it becomes costlier considering the cost involved in the obvious repair works necessitated after a couple of years. Rheda-2000 method acts as a better alternative for construction of washable apron on the platform lines. Though Rheda is a new technology in India and we do not have much experience of it, but on technical perception, it can be said that this technology has enough mettle to bring about a viable solution to this problem. In terms of Railway Board’s letter no. 2004/LMB/14/60 dt. 20.4.05 (Modern/improved design of Washable Apron for railway station), N.F.Railway decided for construction of Rheda-2000 washable apron in Line No.3 of New Alipurduar Division. STEP BY STEP CONSTRUCTION: Ballast less track system currently in use for washable apron, resulting a very low maintenance cost & fail in keeping the washable apron at station P.F. premises clean/hygienic. At present, the 366
indigenous plan of washable apron has not been giving satisfactory performance keeping in view of unhygienic as well as huge maintenance cost. Keeping in view, it has been decided to use ballast-less track with Rheda-2000 technology with VOSSLOH-300 system of fittings which have been approved by RDSO also. It is the true solution to the problem & almost maintenance free track which keeps the station P.F clean & hygienic. i) In REDHA - 2000 technology, the bie - Block sleepers is a steel rain forced pre cast sleepers consisting of two concrete blocks, made of M/55 grade concrete and are connected by two nos. steel Lattice girder. The Lattice girder are protruding from the blocks at both ends and the bottom sides. The structure is supposed to be dedicated to provide a Monolithic integration of precast sleepers with in-situ concrete. ii) Rail Fastenings for ballast less track - VOSSLOH system 300-1 has been used as Rail Fastenings. iii) The Rail in this system used was 60 Kg. Rail. The important design consideration for long term performance of slab track system are: i) The embedding & bonding of the sleeper in-situ slab track concrete. 367
ii) It secures the position of slab against lateral movement i.e. bonding of the slab track concrete with reinforced concrete layer. iii) The bond between the sleeper & the slab track concrete is established by the lattice girder concrete sleeper which is embedded in to slab concrete. This prevents uplift or loosening of the sleepers due to the uplifting wave of the train. PARAMETERS FOR NEW ALIPURDUAR LINE NO.3 i) Scope of work – 560 RM. Washable Apron. ii) Block granted - 68 days iii) Work started on - 31.12.2010 iv) Work completed on - 26.02.2011 Execution of the above work are as follows: PRE ACTIVITIES Step - 1 Inspection and checking of special type sleepers and P.Way Fastenings by the then ADEN/E/APDJ in manufacturing unit at "ANARA" (West Bengal). During checking at manufacturing unit the following checks has been carried out : a) Load Test of Sleeper b) Alignment of Latis Girder c) Physical measurement of all Parameters of Pre-Cast Block Sleeper. d) Material used and its testing reports. e) Cube Test for M-55 Grade Concreting. f) Process of manufacturing of Sleeper. 368
Step -2 (i)
Procurement of materials like ordinary Portland (Gr-53) Cement, Course Sand, Graded Broken Chips, TMT Bars of TATA Steel and stacking on P.F/ Near by to the P.F.
(ii) Procurement of bi-block concrete sleepers with all fastenings (As per VOSSLOH-300/1) at site with due checking of ADEN/E/APDJ. (iii) Availability of 60 Kg. Rail at site. (iv) The spindle support and lateral props for alignment and level the track was also brought at site. (v)
Dismantling of existing water hydrant line and catwalk as it was infringing the layout of proposed Washable Apron.
Step – 3 During Block Activities
1)
Dismantling of 595 Mtr. Track (52 Kg. Rail & PSC Sleeper) at Line No. 3 at PF No-2 has done.
2)
Existing Crib & Cushion ballast are removed by JCB & stack properly at available site. 369
3) Surveying done for fixing up the alignment of Washable Apron with respect to track at both ends, and fixing up the level of proposed Washable Apron w.r.t. existing track and PF. 4) Excavation of earth as per the given layout up to the requisite level has been done by JCB and dumper.
5) The excavated soil base have been compacted by static and vibrating roller. 6)
Spreading granular materials over the soil surface (300 mm thick) by JCB and dumper and compacted layer wise by vibrating roller and soil compactor.
7)
Laying of hydraulically stabilized layer of 300 mm thick M-10 concrete as levelling course has done.
8) Fixing of center Line of track on top of M-10 concrete base by The odolite and Rail level on P.F coping wall surface by dumpy level. 9)
Placing of bottom layer Reinforcement (Longitudinal and transverse) as per drawing. 370
10) Placing of sleeper on bottom layer of reinforcement 11) Placing of top layer reinforcement through the lattice girders of the Twin blocks sleeper. 12) Placing of rail on sleeper.
13) Rough adjustment of alignment as well as level. 14) Installation of spindle supports and lateral props for final adjustment of alignment of level. 15) Providing steel framework with necessary support.
16) Final alignment and levelling of track has been done by using adjustable spindle and lateral props.
371
17) Pouring of M-35 concreting with proper needle vibrator and surface vibrator in 100 Mtr. Strips
18) Finishing of concrete. 19) Loosening of spindle to a quarter turn after 2 to 3 hours of concreting. 20) After One day, Removal of spindles and lateral props by loosening the fastenings. 21) The curing has been done for complete 28 days. 22) During curing period the work of side drain i.e. excavation of earth, formwork, making up reinforcement and M-20 concreting along with fabrication and direction of catwalk has been done. 23) Removal of all from works after curing of concrete. 24) Remedial works have been done as necessary. 25) Converted the FP track to LWR panel by welding of rails and providing of SEJ at both ends of LWR has been done.
372
LONGER TRAFFIC BLOCK The work of construction of Rheda-2000 washable apron was planned and approved for 68 days. The reason for longer traffic block is that Line No.3 is situated on the other side of the station building & approach which is not directly approachable by road. Behind Platform No.3 is a ditch for which making of approach roads is financially not possible. All materials were carried through one inter platform pathway between PF1 and PF2 crossing Line No.1&2. Adequate men and tools provided for ensuring safety of running trains. The work started on 31.12.2010 and track fit given on 26.2.11 after 28 days curing. The total block availed is 58 days. PROBLEMS DURING CONSTRUCTION 1) Catwalk of water hydrant of Platform No.2 had to be dismantled for providing space. 2) Foundation of rail post carrying the hydrant pipe was given special protection during excavation to prevent tilting or infringing to another track. 3) Due care was taken to prevent cutting for S&T cable under the ground. The locations were identified in advance. 4) A speed restriction of 75 kmph was imposed on Line no.2 to avoid damage. PERFORMANCE OF RHEDA WASHABLE APRON AFTER 2 YEARS OF CONSTRUCTION The Rheda2000 Washable Apron in Line No.3 of NOQ was constructed in February’11 with close supervision by SSE, ADEN and Sr.DEN. 373
It is observed that after almost 2 years of construction, the washable apron was found in excellent fettle. There is no sign of defects or deterioration in the concrete sleepers and fittings. Special care has been taken by painting of clips and rail screws at an interval of 12 months.
The track parameters recorded on 20.11.12 are shown here for better appraisal. Km. 144/9145/0
Stn. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Gauge 2 3 1 2 5 3 3 3 2 2 2 2 2 3 3 2 1 2 3 2
XL 1LL L L 2RL 1RL L L L L L 1LL 1LL L L L L 1LL L 1LL L
The versine recorded at every 10 m interval on 20 m chord ranges from (+)3 to (-)3. 374
COMPARISION BETWEEN RHEDA-2000 AND CONVENTIONAL WASHABLE APRON A comparative analysis of construction of Washable Apron by Rheda-2000 technology to the conventional method is done as below to judge the efficacy of the technology: Rheda-2000 technology
Conventional method Initial cost is low Standard of construction is not so good. Gets damaged after 1 – 5 years Gives a standard track geometry Cleaning becomes difficult as normal PSC sleepers protrude over the slab. In case of derailment, ERC and inserts get damaged easily. Sleeper is also to be replaced if only one insert is damaged. Spare fittings like Pandrol Clip, GR pad, liner etc. are easily available 52kg/60kg rails can be used.
Initial cost is twice that of conventional method. Standard of construction is high with special leveling tools etc. Its life is yet to be confirmed, but the results are encouraging. Yields a superior track geometry. Cleaning is easy because there is no protruding body, the sleeper with slab acts as a single monolithic structure. In case of derailment, the plate screws and clips may get damaged which can be easily replaced. Spares are not easily available. 60 kg rail needed along with combination welding if approach track is 52 kg.
Normal PSC sleepers have to be replaced if inserts etc. are damaged but it is a difficult job altogether. NOTE:
1) Speed Restriction of 75 KMPH imposed on main line i.e. Line no. 2 to get rid of the impact of vibration on L/3 working site .
375
2) Special precaution taken by engaging one Flag Man to avoid any Un -occurred incident in carrying the construction materials on P.F. No. 2 by crossing the running tracks. 3) Special care has been taken at the time of fixing centre line as well as fixing level and it has been checked by different engineering officials time to time to achieve the greater accuracy.
WATER SUPPLY ANNEXURE 5.2 Para 531 STANDARDS OF QUALITY OF DRINKING WATER PHYSICAL AND CHEMICAL STANDARDS ______________________________________________________ S.No. Characteristics Requirement Permissible limit (Desirable limit) in the absence of alternate source _______________________________________________________ 1.
Turbidity (NTU scale) 5.0 10
2.
Colour Haten units 5.0 25
3.
Taste and odour Unobjectionable
4.
Ph value 6.5 to 8.5 No relaxation
5.
Total dissolved solids (mg/l) max. 500 2000
6.
Total hardness as CaCo3 (mg/l) max. 300 600
7.
Chlorides as Cl2 (mg/l) 250 1000
8.
Sulphates as SO4 (mg/l) max. 200 400
9.
Fluorides as F (mg/l) max. 1.0 1.5
10.
Nitrates as No3 (mg/l) max. 45 100
11.
Calcium as Ca (mg/l) max. 75 200 376
12.
Iron as Fe (mg/l) max. 0.3 1.0
13.
Zinc as Zn (mg/l) max. 5.0 15.0
14.
Mineral Oil (mg/l) max. 0.01 0.03
15.
Copper as Cu (mg/l) max. 0.05 1.5 Toxic materials
16.
Arsenic as As (mg/l) max. 0.05 No relaxation
17.
Cadmium as Cd (mg/l) max. 0.01 -do-
18.
Lead as Pb (mg/l) max. 0.05 -do-
19.
Residual free chlorine (mg/l) max. 0.2*
_______________________________________________________ Source: Indian Standard - Drinking water - specification (First Revision) IS:10500 - 1991 by BIS *When protection against viral infection is required, it should be min. 0.5 mg/l.
377
EVOLVING ECONOMICAL AND APPROPRIATE DESIGN OF BALLASTLESS TRACK Shiv Om Dwivedi,
Dy CE/Const./Design-1/N.Rly _______________________________________________________ SYNOPSIS The use of Ballastless track (BLT) is increasing world over for want of higher speed and availability of track for operation with least interruption due to maintenance requirements. The initial cost of Ballastless Track (Slab track) is no doubt high (nearly 2 times of ballasted), but its life cycle cost makes it comparatively cheaper in the long run. Further this higher cost shall be seen in the context of overall project cost, where track part is nearly 25%, only. In the present compilation, it has been tried to refer the basic requirements of BLTs, most commonly used around the world. Analysis of the popularity of different types of BLTs gives interesting conclusions that only 3 types of commonly used BLTs (i.e. Bogl, Shinkansen and Rheda) constitute more than 78% of total BLTs constructed in different countries, out of total 34 types having 12300 KMs track total, so far. The speed of train operation has been up to 300 KMPH or more on these tracks. In India, 7 types of different BLTs design, such as in Kolkata Metro (M-1, M-6, M-7 and M-1A type), JammuUdhampur (Slab type), Udhampur-Baramula (Rehda-2000) and Delhi Metro (Simple Beam type)” have been tried, so far. To appreciate the evolution and design of BLT, it is imperative to refer the past experience of nearly 40 years of BLT construction with different design and their benefits as well as shortcomings. Rheda design is free from patent, popular and very flexible for allowing design changes for local conditions. For cost calculation, Rheda’s modified design is taken for comparison, here, as it allows to be used even with the poor soils by using higher percentage of steel in slab for higher flexural stiffness. 379
1.
Basics of Ballastless Track (Slab Track)
The Ballastless track or slab track is basically a concrete or asphalt surface that is replacing the standard ballasted track. This structure is made of stiff and brittle materials, hence the required elasticity can be achieved by inserting elastic components below the rail or/and the sleeper (Lichtberger). Concrete is the prevailing material in slab track applications throughout the world. Only in very special occasions asphalt has been used as material for slab track constructions, and this is due to its high construction demands (Talampekos). Basically, there are two different approaches of slab track design, and these are discrete rail support and continuous rail support (Esveld). There are many different slab track designs based on these approaches. The suitability of a particular slab track design depends mainly at the soil conditions. Each slab track system has different flexural stiffness, which should reckon in according to soil conditions because the whole system depends solely in its bearing capacity. When the soil for instance is soft, a system with high flexural stiffness is needed in order to act as bridge across weaker spots and local deformations in the substructure (Esveld). The whole structure is basically composed of five layers as shown in figure 1, subgrade or subsoil (foundation), frost protective layer, hydraulically bonded bearing layer, Concrete/Asphalt bearing layer, and the rail (Franz).
380
Figure : Usual construction profiles for slab tracks (Darr)
Figure: Basic Comparison of BLT vs Ballasted (UIC-Draft Report - ftp://www.uic.asso.fr/pub/infra/Modificaci%C3%B3n%20puntos%20UIC_0512a.pdf)
1.1 BLT/Slab track requirements The following are the main requirements needed to be understood and considered in selection of BLT and its satisfactory design. 381
•
Subsoil/Sub-grade: The slab track requires stable subsoil basically free of settlements in order to perform efficiently. This is why most times slab track is found in tunnels and bridges (Lichtberger). It is a fact that the scope of adjustments to the track geometry after construction is very limited, hence special preparation of the subsoil before construction is essential (Esveld).
•
Frost Protection Layer: This layer is protecting the upper layers from frost; it can also compensate the differences in stiffness of the various layers towards the subsoil and leads the surface water away rapidly. It is resistant to weathering and frost and is consisted of fine gravel to prevent water from rising from the subsoil. This layer should have very low permeability (Lichtberger). This is similar to blanketing layer being provided.
•
•
Hydraulically bonded bearing layer (HBL) : A hydraulically bonded bearing layer is a mix of aggregates with a bonding agent placed under the concrete or asphalt bearing layer and contributes to an increase in the total bearing capacity of the entire system (Lichtberger). This layer is lying on the frost protecting layer and its average compressive strength after twenty-eight days is 15 𝑁/𝑚𝑚2 (Talampekos).
Concrete bearing layer (CBL)/Asphalt bearing layer (ABL):
It is basically a concrete slab of minimum 200 mm thickness of M35 grade with nominal reinforcement at centre to reduce crack width. This layer may be made out of Asphalt with 300 mm thickness for less vibration and noise in comparison to concrete. Asphalt being sensitive to UV rays needs to be protected by spreading stone chips or gravel. 382
•
Noise Emissions: The slab track produces significantly higher noise radiation compared to the ballasted track. The noise has been observed to be +5 dB i.e. higher than that in conventional ballasted track. The reason is the uncoupling of the rail fastening and the lack of noise absorption by the ballast bed. Hence the higher noise emissions are solely produced due to the nature of the slab track structure. Noise absorbing material, noise protective barriers, acoustically innovative slab tracks (soled sleepers) are some of the proposals, which deal satisfactorily with the noise reduction (Lichtberger).
•
Transition Requirements: Transition points occur in substructures between embankments, bridges and tunnels. There are also superstructure transitions between slab track and ballasted track. Special care is required to be given to such locations, as there will be sudden change of track stiffness. It’s required to be smoothened and safety of a ride as well as no damage of the superstructure of the track to be ensured (Talampekos),
2.
Different slab track systems
The different BLTs/slab track systems developed and used in foreign countries, so far, are tabulated below, which can be divided in two main categories, discrete rail support systems and continuous rail support systems. Further, these two are divided in four and two subcategories respectively. There are total 34 types of Ballastless / slab track having more than 12300 KMs constructed so far with different techniques.
383
Different Ballastless Track Systems Discrete Rail Support With Sleepers or Blocks encased in concrete
Continuous Rail Support
Sleepers on Top of AsphaltConcrete Roadbed (2)
Prefabricated Concrete Slabs
Embedded Rail Structure (ERS)
Clamped and Continuously Supported Rail
(4)
(5)
(6)
Rheda
ATD
Shinkansen
Lawn Track (Rasengleis)
Deck Track
Cocon Track
Rheda-Berlin
BTD
Bögl
FFC
INFUNDO - Edilon
ERL
Rheda 2000
SATO
ÖBB-Porr
Hochtief
BBERS
Vanguard
Züblin
FFYS
IPA
BES
KES
Stedef
GETRAC
BTE BWG/HILTI
SFF
SONNEVILLELVT
WALTER
PACT
Saargummi
(1)
Monolithic Designs
(3)
Heitkamp SBV WALO Table: Different slab track systems (Bastin, Miodrag, Esveld, Lichtberger)
The following is clear from table above: (1) The BLTs shown in bold letters and underlined (top 10 BLTs) constitute 98.7% of total 12300 Kms BLTs constructed in foreign countries. (2) The BLTs of "with sleepers or blocks encased in concrete" type constitute 33.9% of Total 12300 Kms. (3) The BLTs of "Prefabricated Concrete Slab" type constitute 62.2% of total 12300 Kms. 384
2.1 Percentage distribution of different BLTs/Slab tracks abroad The BLT’s lengths (km) constructed around different countries has been given below with percentages to appreciate the popularity. It is clear that the most popular ballastless systems worldwide are the Bögl, Shinkansen, Rheda, Sonneville-LVT, Züblin, Stedef and Infundo-Edilon. S. No.
1
Bögl
Germany
4391
% (out of total 12300.05 Kms) 35.70%
2
Shinkansen
Japan
3044
24.75%
60.45%
3
Rheda family
Germany
2205
17.93%
78.37%
4
SonnevileLVT Züblin
Swiss
1031
8.38%
86.76%
Germany
606
4.93%
91.68%
5
Slab Track Design
Country of design
Total construction (km)
Cumulati ve %
35.70%
6
Stedef
France
334
2.72%
94.40%
7
Infundo-Edilon
Netherlands
211
1.72%
96.11%
8
ÖBB-Porr
Austria
122.2
0.99%
97.11%
9
IPA
Italy
100
0.81%
97.92%
10
PACT
UK
95.4
0.78%
98.70%
11
SATO
Germany
35.8
0.29%
98.99%
12
FFYS
Germany
33.1
0.27%
99.26%
13
BTD
Germany
32
0.26%
99.52%
14
ATD
Germany
31.7
0.26%
99.77%
15
Getrac
Germany
15.3
0.12%
99.90%
16
Walter
Germany
9.4
0.08%
99.97%
17
FFC
Germany
1
0.01%
99.98%
18
Heitkamp
Germany
0.39
0.00%
99.99%
19
BTE
Germany
0.39
0.00%
99.99%
20
BES
Germany
0.39
0.00%
99.99%
385
21
Lawn Track/ Rasengleis
Germany
0.39
0.00%
100.00%
22
Hochtief
Austria
0.39
0.00%
100.00%
23
Deck Track
Netherlands
0.2
0.00%
100.00%
TOTAL
12300 KMs
Table : Total length of various slab track systems constructed worldwide
2.2 BLTs/Slab Tracks used in India So far seven types of BLTs have been used in India, as tabulated below. S.No. 1 2 3 4 5
Type of BLT M-1 M-6 M-7 M-1A Slab Type
6
Rheda 2000
7
Beam Type
Section in which Used Kolkata Metro Kolkata Metro Kolkata Metro Kolkata Metro Jammu Udhampur Rail Link (JURL) Udhampur-Sri Nagar-Baramula Rail Link (USBRL) Delhi Metro Rail corporation (DMRC)
2.2.1 Approval of various BLTs by RDSO S.No
Drawing No.
1
RDSO-BA10054 RDSO-BA10055
2
Details in Drawing
Year of approval Precast RC Ballastless Slab 9.3.1999 0.915 m MBG loading Precast RC Ballastless Slab 9.3.1999 1.22 m MBG loading 386
3 4 5 6 7 8
RDSO-BA10056 RDSO-BA10057 RDSO-BA10058 RDSO/B10061 RDSO/B10061/1 RDSO/M00009 and 00009/1
Precast RC Ballastless Slab 1.83 m MBG loading Precast RC Ballastless Slab 2.44 m MBG loading Precast RC Ballastless Slab 3.05 m MBG loading Rheda 2000 MRT design of BLT track Rheda 2000 MRT design of BLT track Concrete Appron for Specific Requirement at Rly Siding with BLT (GAD) and Reinforcement details
9.3.1999 9.3.1999 9.3.1999 1.8.2003 1.8.2003 17.6.2010
2.3 Brief of Rheda 2000 system and Modified Rheda The first Rheda system to be constructed was in the Rheda Wiedenbruck station (Germany) in 1972. Despite its continuous development, all the designs are based on the original classic Rheda design. The latest modified Rheda has an advantage of suitability even with poor soil having slab of high stiffness due to reinforcement on top and bottom sides. The basic features of Rheda 2000 are given in figure. The Modified Rheda with concept of “Slab Optimization” has been referred to appreciate the structural advantages with different depth variations. The cost comparison with ballasted track having average recent rates of different items has been done, which shows the cost of BLT nearly 2 times of ballasted track, as given in section 3 ahead.
387
Figure: Rheda 2000 on earthworks (Rail One)
2.3.1
Modified Design of Rheda and its Slab optimization
The reinforcement in most of the slabs is applied in the neutral axis just for crack control purposes. An alternative and modified design for slab track, based on Rheda 2000, has provided combined thick slab with reinforcement at top and bottom both to enhance its bending stiffness to take care of poor soil as well as crack growth. This will save expenditure substantially incurred for soil improvements. It has been observed by Esveld that a typical reinforcement of 1.2 to 1.5% used in concrete slabs increases stiffness sufficiently. The optimization of slab thickness hslab has been carried out through research by Esveld with different combinations of soil parameters, thickness variations and steel variations.
388
(Figure: Original Rheda verses modified design) Ref: (http://www.esveld.com /Download/TUD/ANT187 Keynote_Esveld_web.pdf)
From research of Esveld, it has been observed that a slab with a reinforcement of 1.2 % and thickness of 30 - 35 cm requires a substantial soil improvement (the foundation modulus should be greater than 0.11 N/mm3, or Ev2 > 100 N/mm2). On the other hand slabs with the thicknesses of 40 to 50 cm can be applied on soil of moderate and even poor quality, with C > 0.05 N/mm3, or Ev2 > 30 N/mm2. If a reinforcement percentage of 1.5% is used then the slab thickness can even be reduced to values in the order of 30 cm. Further to appreciate the advantage of Rheda over others, reference is available in UIC publication ‘application and experience with ballast less track, published in 2005, in which it is expressed for new line construction between Amsterdam and South Europe, that“despite the extensive experience gained with ballastless track in the Netherlands it was decided, for this particular highspeed line, to use a ‘proven’ high – speed construction concept called Rheda 2000”. This line has been in operation since 2009.
389
2.4 Other Designs of BLTs (With Sleepers or Blocks encased in concrete) The following are the some other popular design with Sleepers or Blocks encased in concrete. 2.4.1 ZÜBLIN system:
Figure: Most recent developed Züblin system (Züblin)
2.4.2 Stedef
Figure : Classical and recent developed Sateba S312 Stedef System (UIC report). 390
2.4.3 Sonneville-LVT
Figure : Sonneville track used in the Eurotunnel (Bilow,Gene & Randich)
2.5 Designs with “Sleepers on Top of Asphalt-Concrete layer” type Due to the asphalt properties, these systems can perform slight plastic adaptations when it is needed. According to Esveld, when higher pressures occur below certain sleepers than others, asphalt will deform because of its visco-elastic properties until a new equilibrium has been established leaving the pressures more levelled. Few more positive features of these systems are that allow exchange of sleepers in case of damage and generally are easily maintained. However, these methods collectively been used in total 150 kms (1.25% of total 12300 Kms), so far, and cannot be considered as popular. 2.5.1 ATD system
Figure : ATD system design (Darr & Fiebig) 391
2.5.2 BTD System
Figure : BTD construction version 2 (V2) (Darr & Fiebig, Franz).
2.6 Prefabricated concrete slabs: This slab track category is consisted of reinforced or pre-stressed concrete slabs preserving constant and safe inclination and gauge of the two lines of rails simultaneously (UIC report15). Prefabricated slabs can be found in many places around the world, e.g. Japan, Germany, Italy, China and Taiwan. Total 7500 Kms (nearly 60% of 12300 Kms) of such track have been laid, so far. The cost of prefabricated concrete slab design have been observed to be nearly 4 times in comparison to ballasted track (Lichtberger). Most popular systems include Shinkansen and Bögl systems. 2.6.1 Shinkansen system
Figure: Shinkansen slab track (Bastin)
392
2.6.2 Bögl System
Figure: Max-Bögl track system (Bastin)
2.7 Monolithic Designs 2.7.1 PACT system
Figure: PACT slab track system (Bastin) 393
2.8 BLTs with Continuous Rail Support System When the rail is continuously elastically supported by the concrete bearing layer either embedded or clamped then it belongs to the continuous rail support systems as shown below. The most popular design of continuous rail support system is INFUNDOEDILON design, which is intended mainly for urban passenger rails (subways, tramways) (Esveld). 2.8.1 INFUNDO-EDILON system
Figure: Embedded rail construction INFUNDO (Esveld)
3 Slab Track Costs The Cost of initial construction, saving in maintenance cost and higher speed potential have been the major consideration in the choice between Ballastless track and Ballasted track. The other considerations include the possibility of repair after major derailment on Ballast less track, which have been addressed to good extent in a project carried out by Railway Officers during Sr. Professional Course/IRICEN, available at website. 394
The advantage of slab tracks to perform for longer time without significant amount of maintenance comparing to conventional ballasted track has long been evaluated by different researchers. Results from one such evaluation in this subject has been reproduced below. (Rudolf & Dirk). The advantage of slab tracks to perform for longer time without significant amount of maintenance comparing to conventional ballasted track has long been evaluated by different researchers. Results from one such evaluation in this subject has been reproduced below. (Rudolf & Dirk). Further similar study can also be carried out for actual cost of maintenance activities in Indian Railways and a similar graph can be plotted to appreciate the cost effect of BLT vs Ballasted track.
Figure: Time depending value, ballasted track and slab track (Rudolf & Dirk)
The RHEDA design, which has been found to be most economical among other designs, is considered to be most popular in many counties including India. The cost of Rheda comes out to be approximately 2 times more than the ballasted track design as per calculations carried out in Indian context, as given below.
395
4 Conclusions & further recommendations The increasing trend of use of Ballastless track/Slab track itself advocates its comparative advantage over ballasted track. Accordingly, the merits and demerits of BLT vs Ballasted track have 396
not been covered in this article. However, the basics terms of BLTs have been deliberated in brief such as Subsoil, Frost protection Layer, Hydraulically bonded layer, Concrete bearing layer/Asphalt bearing layer, Noise emission and Transition requirements. Different types of BLTs used in foreign countries with length of such stretches including percentage of each type out of total length clearly shows the popularity of two basic types of BLTs, i.e. “with sleepers or blocks encased in concrete” and “Prefabricated Slab type”. Further, Prefabricated Slab type BLT is costly in comparison to the former. In the former type (i.e. “with sleepers or blocks encased in concrete”) the most popular type is the Rheda 2000 and modified design of Rheda as explained with advantage of use with even the poor soil conditions (with Ev2 up to 30 N/mm2) makes it more suitable in Indian conditions for being comparatively cheap also. The different types of BLTs used in India have been tabulated for ready reference including approved drawing from RDSO for necessary feedback of performance and maintenance requirement to evaluate the proposal of same in new constructions. In Netherland also, after various trails of different types of BLTs, Rheda 2000 has been preferred over others for their latest high speed track connecting Amsterdam with the London and rest of South Europe for which construction started in 2005 and train operation started in 2009 with speed of 300 km/h even though the soil quality is considered poor. In reference in higher cost of BLT, it may be appreciated that the track costs only about 25% of cost of overall project, therefore even its being twice costlier than ballasted one increases overall project cost by 25%, only. The BLT’s advantages of least maintenance, quality of ride, uninterrupted availability of track for operation makes sense to go for BLT in present scenario of higher technology and shortage of manpower. The use of BLT in DMRC, Delhi, line no. 1 is in operation for the last 10 years without any significant maintenance requirements. 397
It is therefore recommended that Modified design of Rheda shall be used in different type of soils, initially, for few construction projects in Indian Railways for new line construction or doubling projects, as this seems to be the least costly and quite popular after evolution in the last 40 years. References 1. Slab Track Systems for High-Speed Railways ,Master Degree Project, Georgios Michas, Division of Highway and Railway Engineering, Department of Transport Science, School of Architecture and the Built Environment, Royal Institute of Technology, SE-100 44 Stockholm, Sweden, TSC-MT 12-005, Stockholm 2012 2. Feasibility_study_Report_march_2002,UIC Infrastructure commission civil http://www.uic.org/IMG/pdf engineering support group. /Feasibility_study_Report_march_2002.pdf 3. Application and experience with Ballastless track, Feasibility_study_Report_march_2005, UIC Infrastructure commission civil engineering support group. 4. Approved drawings of various BLTs by RDSO , Lucknow. 5. UIC-DraftReportfttp://www.uic.asso.fr/pub/infra/Modificaci%C3%B3n%20puntos%20UIC_0 512a.pdf 6. Critical Study of Ballastless Track of Kolkata Metro Railway:http://wiki.iricen.gov.in/doku/lib/exe/fetch.php?media= ijce_december_09:5_dec_09.pdf 7. PROJECT REPORT ON CRITICAL STUDY OF BALLASTLESS TRACK OF KOLKATA METRO RAILWAY: http://wiki.iricen.gov.in/doku/lib/exe/fetch.php?media=9209:vkverma.pdf
398
OVER VIEW ON BALLAST LESS TRACK IN MRTS/CHENNAI S. Vijayakumaran, CAO/CN/MS P. Kalimuthu, CE/MTP(R)/MS R. Ravikumar, Dy.CE/MTP(R)/MTMY _____________________________________________________________
Introduction: Traditionally, Railway track consists of rails laid on timber, steel or concrete sleepers supported by a ballast bed. Ballast is a prime component of the track that acts as a vibrant medium to transmit from the rail surface the weight of the train down to the formation. It ensures a cushioned and smooth run for the train and precludes the longitudinal displacement of the rail called creep. Though ballasted track has many advantages it has its own disadvantages when it is laid in Tunnel, P.F lines and in Suburban lines. To overcome these defects alternative solutions were tried and one such solution like ballast less track (BLT) was evolved after many years of experience and research. In MRTS system/Chennai, Ph-I between Chennai Beach to Tirumailai, track was laid with ballast. For PH-II, between Tirumailai to Velacheri, it was with BLT. Further PH-II extension between VLCY to STM, it is planned with BLT and the work is in progress. In this article the advantages and disadvantages of BLT and the method adopted to ensure proper quality in laying BLT is dealt in detail. 1.0
BALLASTED TRACK:
Few main advantages of Ballasted Track are as given below: 1. Relatively low construction cost. 2. High elasticity 3. High maintainability at relatively low cost. 4. High noise absorption 399
However, it has a number of disadvantages, out of which few are given below: 1. The track tends to float, in both longitudinal and lateral directions in long run, as a result of non-linear, irreversible behavior of the materials. 2. Limited non-compensated lateral acceleration in curves occurs, which is due to limited lateral resistance offered by the ballast. 3. At high speeds ballast can be churned up, causing serious damage to rails and wheels. 4. Irregular settlement due to improper packing of ballast etc. 5. Defects development at critical locations - P&C, joints, SEJ, LC’s. 6. Damage of Ballast at places with irregularities eg. Rail defects, welded joints, insulated rail joints, bridge approaches. 7. Deep screening after every 10 years or lesser periods.
2.0
BALLAST LESS TRACK:
2.1 In ballast less track (BLT), as the name suggests, the ballast is replaced by a bed of concrete. Rail traffic is reaching out toward new horizons on ballastless track systems. The arguments are indeed convincing: long life cycles, top speed, ride comfort, and great loadcarrying capability. You take no chances with these systems, especially with newly constructed lines: even at speeds over 300 km/h, your coffee will stay in your cup. Practically maintenance free, ballastless track systems ensure almost 100% availability over many years. In many cases, a maintenance-free track system is indeed the more cost-effective solution over the long run.
400
In the ballast less tracks followed in MRTS / Chennai, the rails rest on rubber pads placed over plinth beam, which are fixed on to the concrete bed. This is a well proven design used in more than 10 metro train projects across the world and in different gauges. The continuous plinth track system provides a continuously supported base to the rail with discrete shoulders retained by rail clips. The BLT demands: a)
Efficient drainage system
b)
Transitions to be designed
c)
Advance planning for signaling and track circuiting.
2.2
IT’S MAIN ADVANTAGES ARE:
•
High operational availability as less or no maintenance
•
Reduced maintenance cost
•
Reduced traffic blocks
•
Less construction depth 401
•
Dust free (Eco friendly)
•
Road rescue vehicles can ply over BLT in tunnels
•
Less noise pollution.
•
Higher resistance to lateral and longitudinal forces permitting steeper grade and higher speed.
2.3
IT’S MAIN DISADVANTAGES ARE:
•
Requires high precision laying and expert supervision.
•
High cost of construction- about 1.5 to 2 times over the conventional Ballasted track.
•
Derailments can cause costly damage.
•
Repair work is more complicated Once the BLT is laid geometrical parameter like cant, curvature, transition cannot be changed.
3.0
TRACK ASSEMBLY
3.1 In MRTS PH-II Vossloh fittings were adopted and were laid in 2007 and its performance is satisfactory. For PH-II Ext. between VLCY to STM, PANDROL Double resilient base plate assembly is adopted. This system satisfies the technical parameter requirement fixed by Railway Board vide letter No. 2003 / Proj / Bangalore / 2 / 2 (Pt) / Dtd. 28.4.2011. This system is also adopted in the following Railway systems. The various components of pandrol double resilient base plate assembly are given below: 1.
Conforming Shim
2.
Base Pad
3.
Base Plate
4.
Anchor Stud 402
5.
Nyloc Nut
6.
Rail Pad
7.
Insulator
8.
Compression Spring
9.
Plastic Collared Washer
10 . Eccentric Nylon Bush 11 . Pandrol Clip 11
6
7
3
5
6 7 8 9
10 11 3.3
Performance criteria laid down by the Railway Board
3.3.1
General:
1. The fastening shall be designed to hold the two rails of the track strongly to the supporting structure in upright position by resisting the vertical, lateral and longitudinal forces and vibrations. 403
2. The fastenings shall be with a proven track record. Fastening system should have satisfactory performance record of minimum five years in service in ballastless track on any established railway system. 3. The fastening shall provide insulation to take care of return current of traction system. 4. Fastening should satisfy the required performance norms as stated in the following paragraphs. 3.3.2 Following are the technical performance requirements of fastenings: The fastening shall, i). Have design service life of 30 years in general. However, its components such as rubber pad, rail clip etc. can be designed for 300 GMT or 15 years whichever is less. ii). Have dynamic/static stiffness ration of 1.4(max.) Dynamic stiffness to be tested as per EN 13481 – 5 Annex B. Ratio can be calculated by dividing the dynamic stiffness to static vertical stiffness (to be calculated as per S.No.2 of para). iii). Have clip toe load 18KN per rail seat in service (i.e. even after creep etc.) 3.3.3 Fastening system (bonded or non-bonded) assembly shall be designed for static vertical stiffness of less than 35KN/mm (in the secant range 5-80 KN) as a whole when tested using the specification EN-13146-4: 2002 Railway application-track-test methods for fastening. 3.3.4 The Rail fastening system shall be tested to the following specification for different technical parameters and should meet the acceptance criteria as mentioned in the following table. 404
Sl. No 1
2
Technical Parameter Determination of longitudinal rail restraint
Test Method EN13146-1 (latest version)
Acceptance Criteria 7 KN(min.)
Vertical stiffness complete fastenings system.
EN13146-4 (latest version)
35KN/mm (max.)
No sliding,yield or cracking is allowed for the fastener parts.
of
Remarks This has to be tested before repeated load test.
3
Determination of clamping force.
EN13146-7 (latest version)
18 KN (mini.)
This has to be tested before repeated load test.
4
Determination of electrical resistance
EN13146-5 (latest version)
5 KΏ (mini.)
The electrical department may specify a higher value for use with certain track circuit.
5
Effect of severe environmental conditions
EN13146-6 (latest version)
The fastening system shall be capable of being dismantled without failure of any component using manual tools provided for this purpose after exposure to the salt spray type.
405
6
Effect repeated loading
of
EN13146-4 (latest version)
No wear deformation
or
Test load and fastening position will be taken as per EN-13481 - 6
6A
On vertical stiffness
EN13146-4 (latest version)
Variation less than 25% of the initial value
No sign of bond failure/fracture/seepage
6B
On longitudinal rail restraint
EN13146-1 (latest version)
Variation less than 20% of the initial value
Except rail and fastener, no sliding yield or cracking is allowed for fastener parts. The longitudinal load/ deformation curve shall fall in the envelope of upper and lower limit which is to be submitted along with test report.
6C
On clamping force
EN13146-7 (latest version)
Variation less than 20% of the initial value
3.3.5 Testing of Track Assembly & components used in Phase II Extension Project : The following tests has been carried out at Pandrol UK Laboratories, UK by this railway. Sl. No 1. 2. 3. 4.
Test
Specification
Assembly Dynamic Stuffiness Clamping Force-Pre RLT Longitudinal Restraint-Pre RLT Static Vertical Stiffness –Pre RLT 406
BS EN 13146-9:2009 BS EN 13146-7:2012 BS EN 13146-1:2012 BS EN 13146-9:2009
5. 6. 7. 8. 9. 10. 11.
Repeated Load Static Vertical Stiffness –Post RLT Longitudinal Restraint-Post RLT Clamping Force-Post RLT Dynamic / Static Stiffness Ratio Electrical resistance Effect of server environmental conditions Vertical load for cast-in components (Pull out test) Fatigue test of tension Clamp Stiffness test static – of Elastic Base plate Pad Stiffness test Dynamic – of Elastic Base plate Pad Fatigue test of Assembly as a whole Clip Toe load
12. 13. 14. 15. 16. 17.
3.3.6
BS EN 13146-4:2012 BS EN 13146-9:2009 BS EN 13146-1:2012 BS EN 13146-7:2012 BS EN 13146-9:2009 BS EN 13146-5:2012 BS EN 13146-6:2012 BS EN 13481-2 Annex A:2012 BS EN 13146-9:2009 BS EN 13146-9:2009 BS EN 13146-4:2012
Registers maintained:
The following registers are maintained for this purpose and the Performa of the register is as shown in annexure. 1. Checklist for Track parameters 2. Checklist for Reinforcement at site 3. Material passing register 4. Cube strength register 5. Quality control register 6. Cement consumption register 7. Steel consumption register 8. RMC Register. 407
3.3.7
Results after construction
Grider No/Plinth no
Sleeper No
Gauge
Cross level
4/1
1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6
N -1 N +2 N N N N +1 N -1 N +1 N +1 +1 N +1 +2 +2 +2 N N N N N N N -1 N
L L L L L L L L L RL1 L L L L L L L L L L L L L L L L L L LL1 LL1
4/2
4/3
5/1
5/2
Twist (3m)
Rail Cant
Long. Alignment (20m)
0 0
1mm
-2
+1
408
Remarks
4.0
Construction and quality control measures in execution of ballastless track.
As already indicated the system fixed is highly rigid and cannot be altered for geometric correction during maintenance, the laying of BLT has to be done with high precision. The quality control measures adopted during execution in MRTS/Chennai is explained below. Various steps involved in construction and checks done are explained here: 1. Shear Connectors. 2. Alignment of Track. 3. Gauge Support Frame. (GSF) 4. Rail Cant. 5. Gauge. 6. Cross Level. 7. Twist. 8. Reinforcement. 9. Shuttering for Plinth Beam. 10. RCC Guard Rail 11. Concreting and curing 12. Rail welding 13. Quality Control checks. 1. Shear connectors:
409
Shear connector consists of 12 mm dia at 150mm c /c are embedded in the girder and left protruding the surface. The shear connectors are brought to its correct position before commencement of the work. 2. Alignment of track:
The alignment of track is an essential parameter to be maintained for smooth operation of trains which in turn gives safety and comfort to the travelling public. Hence while laying the track this parameter is to be checked thoroughly and every care needs to be taken to ensure that the track is laid with-in the tolerance permitted. Unlike in conventional track this parameter cannot be altered beyond certain limit after laying and following actions are taken to ensure proper Alignment. i) The surface of the PSC girder is cleaned and made free from dust and other foreign materials. ii) The center line of track is marked by theodalite from the pre determined points and marked permanently. 410
iii) For straight track the alignment is struck on the top surface of girder for about 500 m with centre points at every 25 m intervals with paint. These points at 25 m intervals are connected by doted lines with permanent marker. Rails are placed longitudinally temporarily supported on wooden blocks at 4 m intervals 300 mm above girder level. The LHS side rail is taken as reference rail. From centre line of marking to the Gauge face of rail is kept as 0.875 (1.75/2) using plumb bob. Longitudinal gradient of 1 in 100 is marked on the side kerb at 22.5 m intervals. The spacing of dummy plate at 750 mm c/c is marked with paint on both rails. Dummy plate is fixed with rail at 750 mm interval by screw bolt on both sides. The anchor stud and nylon nut is fixed with dummy plate 2 numbers in straight track and 4 numbers for curved track. The anchor stud is embedded in concrete for a depth of 149 mm and protruding 121 mm above the top of concrete. Length of stud bolt is 270 mm and dia 27 mm. The unevenness of rail is checked with leveling instrument at GSF location upto 1 mm accuracy. In curves, the level of inner rail is taken as base rail and adjusted first – then the required super elevation is provided on the outer rail. The plinth beam has been designed and constructed to suit the super elevation at the curved portions. The horizontal versine is checked with the help of holders and piano wire with 20m chord at 10m intervals and after that, just before concreting the gauge and alignment are once again checked. 3. Gauge support frame (GSF) The overall length of PSC Box girder is standardized to 22.5 m and to have better quality control, this 22.5 m girder is divided into 5 bays with 0.15 m gap. The GSF is placed at 4.5 m interval in the bay gap and holding both the rails at 500 mm above girder. 411
Vertical Stud bolt Horizon tal
Cant adjustment The gauge support frame is a device used to adjust and maintain the gauge, vertical level of rail table, rail cant (1 in 20) at the time of concreting. The above adjustments are made in the following manner: i.
Rails are lifted up and down by rotating the vertical stud bolt, clockwise for lifting up and anti clockwise for lowering.
ii.
The stud bolt is of 40 mm dia MS bolt and having a height of 720 mm. (threaded to 350 mm, plain portion 340mm and hexagonal nut head 30 mm.
iii.
Rail cant adjustment by screw bolt on the inner side of the rail.
4. Rail Cant: Rail cant with 1 in 20 is maintained by taking levels on both sides of rails in the dummy plate in GSF location. Longitudinal alignment of reference rail (LHS) is corrected by theodalite. 412
5. Gauge:
The gauge is checked with special type gauge that is fitted with stool of height 100mm. The RHS rail is adjusted to bring the track to the required gauge of 1673 mm with stud bolt in GSF. The movement of GSF is arrested horizontally by the adjustable side support jack on both sides. 6. Cross level:
413
The RHS rail is adjusted to the correct level by rotating the vertical stud bolt, clockwise for lifting up and anti clockwise for lowering. 7. Twist:
The twist is checked with gauge at 3 m intervals and records are maintained. 8. Reinforcement: Reinforcement is checked to ensure that it is provided as per the approved drawing and standard RCC register are maintained..
414
9. Shuttering for plinth beam:
Steel shutters of 4.35m length is fixed to 230 mm height on outer side and on inner side the shuttering height is kept as 450 mm. Placing of shutter - the inside bottom is supported with wooden runner with cross bracing of casuarina poles and top with MS flat with bolt nut at require spacing. The outside bottom is supported with wooden runner with horizontal support by casuarinas poles at top and bottom. M 35 concrete is poured for RCC plinth beam and RCC guard rail concrete is done on next day. 10. RCC guard rail Unlike in conventional track concrete beam acts as the guard rail in place of rails. The concrete wall is constructed throughout. 415
Electrical circuit continuity is provided at guard rail end with MS flat160x40x8mm welded with reinforcement (for the purpose of signaling). 11.
Concreting and curing:
i.
RMC Concrete of M35 is used with Water cement ratio of 0.44
ii.
Slump @ site is 70 -80mm maintained for which Admixture of 0.80% is added. 416
iii.
Compaction is done by Needle vibrator of size 40mm & 25mm
iv.
Curing is done by ponding and wet gunny bag with continuous pouring of water.
12.
Rail welding:
Rails are welded at site by mobile flash butt welding to form continuous welded rails. 13.
Quality control checks
Just before concreting all parameters are once again checked for the confirmation for cross levels, gauge, alignment of rail, top level & rail cant and immediately after concreting all parameters are finally checked. Executed portion of track in MRTS PH-II extension:
417
6.0
Conclusion
Even though the initial cost for construction of ballast less track (BLT) is more than the ballasted track, considering the advantages of safe running, less maintenance cost, reduced traffic block, dust free, eco friendly and reduced noise pollution, hence ballast less track is preferred over the ballasted track. Quality control in construction, particularly the BLT, is of paramount importance as BLT does not have much tolerance and does not permit much variation. All efforts put in by way of development of proper system of QAP before the work is taken up has helped in achieving good quality BLT which in turn will give trouble and maintenance free track for years.
418
REHABILITATION OF WASHABLE APRONS USING ACCELERATED EARLY HIGH STRENGTH MICRO CONCRETE - D. Anjaneyulu Reddy, Sr.DEN/Co-ord/SC, SCR - K. Mutyala Naidu, DEN/Central/SC,SCR - D.Venkata Ramana, SSE/Works/HYB,SCR
___________________________________________________________________ Introduction: Washable aprons are the essential part of any station where the trains originate/terminate/ halt for long durations to maintain the hygienic environmental conditions. Secunderabad Division has got as many as 16 nos. of washable aprons out of which 9 nos. are at Secunderabad, 5 nos. are at Hyderabad and 2 nos. are at Kazipet stations. The basic structure of these washable aprons is placing the PSC track sleepers over a RCC raft bed duly filling the space between sleepers with concrete to a slope of 1 in 20 towards a drain. These aprons are supposed to take only coaching traffic at low speeds upto 15KMPH. But due to the operational requirements / constraints these washable aprons are subjected to goods traffic also. There is heavy movement of Mail/Express trains, MMTS trains along with CC+8+2 goods train traffic over these aprons leading to sharp deterioration of the health of the washable apron. Some of these aprons are situated in sharp curves of upto 5.5 where damage to PSC sleepers at seating area is very often leading to spread gauge and then to derailments which affects traffic, at busiest yards like SC and HYB, to such an extent that system comes to halt. To avoid these derailments and to maintain these aprons to safe standards is becoming a Hercules task to Section 0
419
Engineer (Pway) with the limited sources he had, unless the damaged sleepers are replaced with new/ serviceable sleepers. Added to the above, traffic block was a constraint to attend any repairs to aprons and to replace the damaged sleepers in the running track. Replacing the damaged sleepers involves breaking the apron around the sleeper, removing the damaged sleepers, cleaning loose materials in the bottom and sides, placing the new sleeper and providing filling concrete to the required profile.
Carrying out these above operations using ordinary cement needs traffic block for a period of 10 to 12 days which is a major problem in a busy station like Secunderabad. To avoid this problem a reformative approach was found to tackle the problem of replacing isolated broken sleepers with minimum traffic block using accelerated very early / early high strength micro cements which has yielded good results. 420
2.1 Statement of the problem : Due to heavy goods traffic, Mail/Express and MMTS trains movement, apron on road no.3 of SC yard was damaged at isolated locations particularly in sharp curve area at HYB end for a length of around 32.5m. 43 sleepers were damaged completely at rail seating due to crushing action and heavy lateral thrust, which lead the track parameters to go beyond tolerances. Due to this, two derailments were also occurred in the same location and goods traffic was also suspended on road no.3 till attention. Pressure was upon engineering department to attend the broken sleepers within a minimum time and restore goods traffic in the overall interest of the Railways. It was observed that the entire remaining length of apron of Rd. no.3 is in a very sound condition which is in straight portion except 32.5m length of apron in a sharp curve, which is completely in damaged condition and warranted urgent replacement of broken sleepers. As the block period available is very less, replacing sleepers using ordinary cement is not possible. Hence the sleepers need to be replaced using the accelerated very high early strength flowable micro cements like Conbextra HES, Conbextra GP2 etc., of Fosroc. 2.2 Approach: Apart from using ordinary cement, two options are found suitable, in replacing the broken sleepers, using two products of Fosroc, named as Conbextra HES and Conbextra GP2, for different block periods available at site. • Using Conbextra HES requires a minimum block period of 8 hours (The block period shall be increased suitably depending on the no. of sleepers being replaced at a time), if breaking and removing the damaged sleepers is carried out in pre-block operation. • Using Conbextra GP2 requires a minimum block period of 30 hours (The block period shall be increased suitably depending on the no. of sleepers being replaced at a time), if breaking and removing 421
the damaged sleepers is carried out in pre-block operation. Considering the heavy traffic at SC yard and block constraints option 1 was chosen for replacing 31 sleepers and option 2 was chosen to replace about 40 sleepers. Considering the economical aspect both Conbextra HES and Conbextra GP2 mix (added with 100% stone chips of size 5 to 10 mm) is used for filling the gap between bottom of sleeper and top of raft bed and the remaining portion (filling concrete) up to top of apron was filled with ordinary cement concrete 1:1:2 (nominal mix of 1cment, 1 river sand, 2 graded stone chips of 20mm size) added with Conplast NC, which is an accelerator for quick setting and early strength of cement. 2.3 Methodology: CONBEXTRA HES / CONBEXTRA GP2 can be used as per the availability of block time. CONBEXTRA HES is suitable where ever the block constraint is very high. This is used where block availability is of 8 hrs. as it attains Compressive strength of 32 N/mm2 in just 3 hours when mixed with 100% stone chips of size 5 to 10mm. 2.3.1 Properties of Conbextra HES Setting time at 270C (IS 5513) Initial
11 - 14 minutes
Final
15 - 17 minutes
Compressive strength : (BS 1881:Part 116) in N/mm2 Age (days)
Pourable consistency (W/P 0.21)
1 hr
14
422
3 hr
29
6 hr
34
24 hr
41
3 days
40
7 days
51
28 days
59
Special precautions for application Pre-soaking Several hours prior to placing, the concrete substrates should be saturated with fresh water. Immediately before grouting takes place any free water should be removed with particular care being taken to blow out all bolt holes and pockets. Mixing For best results a mechanically powered grout mixer should be used. When quantities up to 30kg are used, a slow speed drill fitted with a high shear mixer is suitable. To enable the grouting operation to be carried out continuously, it is essential that sufficient mixing capacity and labour are available. The use of a grout holding tank with provision to gently agitate the grout may be required. Note: When required to grout at high ambient temperatures, Fosroc recommends usage of cold water maintained at 50C. The selected water content should be accurately measured into the mixer. The total content of the Conbextra HES bag should be slowly added and continuous mixing should take place for 5 minutes. This will ensure that the grout has a smooth even consistency. 423
Placing At 300C place the grout within 10 minutes of mixing. Conbextra HES can be placed in thicknesses up to 50mm in a single pour. For thicker sections it is necessary to fill out Conbextra HES with well graded silt free aggregate to minimise heat build up. Typically 5 to 10mm size coarse aggregate is suitable. Coarse aggregate weight of 50 – 100 % of Conbextra HES can be added, depending on the thickness to be applied. Continuous grout flow is essential. Sufficient grout must be prepared before starting. The time taken to pour a batch must be regulated to the time to prepare the next one. The uniformly mixed grout should be placed using a suitable grout pump for fast application. Curing On completion of the grouting operation, the grout should be left for air drying. However membrane curing agent or polythene sheet may be used to give an early surface protection from precipitation. But never cure the grout with water. 2.3.2 Properties of Conbextra GP2 Setting time at 270C Initial
20 minutes
Final
120 minutes
424
Compressive strength : (BS 1881:Part 116) in N/mm2 Age (days) Flowable consistency Pourable consitancy (W/P 0.18) (W/P 0.165) 1
24
27
3
45
54
7
55
66
28
65
78
Compressive strength with addition of aggregates in (N/mm2) W/P 0.18
% of aggregates ( IS 516 - 1959)
Age(days)
50%
75%
1
28
30
3
50
52
7
60
63
28
70
75
Special precautions for application All the precautions are similar to Conbextra HES with deviations as given below. When the air or contact surface temperatures are 100C or below on a falling thermometer, warm water (30 - 400C) is recommended to accelerate strength development. 425
At ambient temperatures above 400 C, cool water (below200C) should be used for mixing the grout prior to placement. Curing On completion of the grouting operation, exposed areas should be thoroughly cured. This should be done by the use of Concure WB curing membrane, continuous application of water and/or wet hessian. 2.3.3 Properties of Conplast NC Conplast NC is guaranteed completely free of all forms of chloride and is supplied as a light straw coloured liquid. The main active ingredient is an inorganic formate. Compatibility with cements: May be used with all types of Portland cements. Not suitable for use with high alumina cement. Portland cement of 53 Grade is recommended. Acceleration: The addition of Conplast NC to Portland cement concrete mixes accelerates both the setting and rate of strength gain. The strength improvements are most significant during the first 18 hours. Long term effects: Accelerated corrosion testing of steel in concrete has shown that Conplast NC does not affect the protection of steel afforded by cement against corrosion even at four times the normal dose level. Dosage: The recommended dosage range for standard concrete and mortar mixes with all grades of Portland cement is 2.0 to 3.0 litres per 100 kg cement. Mixing: Conplast NC should be stirred before use. Conplast NC should be added direct into the mixer. Best results are obtained when added at the same time as the mixing water.
426
Typical effect of Conplast NC on strength gain (may vary depending on the mix used.):
Curing Temperature
Compressive strength (N/mm2) 10 18 24 3 7 hrs hrs hrs Days Days
Conplast NC Dosage in Litres/100kg
Initial set hrs.
Final set hrs.
Nil
3
4
1.0
4.5
6.0
17.0
29.0
2.5
2
3
3.5
9.0
11.0
24.0
36.0
200C
Sleeper CC 1:1:2 + Conplast NC Surface brushed with –Nitobond SBR Conbextra GP2 • When block availability is of 3 - 4 days Sleeper CC 1:1:2 + Conplast NC Surface brushed with –Nitobond SBR Conbextra HES • When block availability is of 6-8 hrs 2.3.4 Material & Equipment required: • Conbextra HES / Conbextra GP2 • Conplast NC • Well graded and thoroughly cleaned 5-10mm size aggregate for mixing with Conbextra HES/ Conbextra GP2. 427
• Well graded and thoroughly cleaned 20mm graded material for nominal mix of 1:1:2 for using in filling concrete. • Tractor mounted compressor to break the apron • Mixing equipment • Tubs for mixing and pouring of mix. • Ice Cubes to mix in water (to keep temperature of water < 200C) • Air blower to clean the dust n loose material • Quantity required for 1m3 of Conbextra HES mix adding 100% of stone chips by weight: • Conbextra HES – Yields 9liters pourable liquid from 15 Kg bag. • Consider equal quantity of stone chips of 5 – 10mm size. • Assume that 1.2m3 of partial dry contents will yield 1m3 of concrete i.e 60% of each. • Quantity of Conbextra HES required for 1000 liters = 1000 / 9 x 15 = 1666.67kgs. • Quantity of Conbextra HES required for 1m3 = 1000 / 9 x 15 x 60 / 100 = 1000 kgs. • 5 – 10 mm stone chips required for 1 m3 = 1000 Kg. • Quantity required for 1m3 of Conbextra GP2 mix adding 100% of stone chips by weight: • Conbextra GP2 yields 12.5 liters pourable liquid from 25 Kg bag. • Consider equal quantity of stone chips of 5 – 10mm size. • Assume that 1.2m3 of partial dry contents will yield 1m3 of concrete i.e 60% of each. • Quantity of Conbextra GP2 required for 1000 liters = 1000 / 12.5 x 25 = 2000kgs. • Quantity of Conbextra GP2 required for 1m3 = 2000 x 60 / 100 = 1200 kgs. • 5 – 10 mm stone chips required for 1 m3 = 1200 Kg. 428
2.3.5 Pre block operations : • Working out Number of PSC sleepers required and transporting them to site well before block. • Loosening of seized ERC / fittings. • Arranging abrasive cutter for rail cutting and labour for dragging of rails.(This operation is not required when there is possibility of removing / inserting the sleeper with / without lifting the rails. • Keep ready the required no. of compressors on PF with good working condition. • Keep ready sufficient quantity of Conbextra HES / Conbextra GP2, 5 - 10 mm size and 20mm well graded coarse aggregate filled in bags as per the requirement for mixing with one bag of modified cement, after washing with clean water free from dust and other loose materials. • Keep ready the mechanical mixing equipment. • Keep ready the tubs for concrete mixing and measuring cans for mixing water. • Ice cubes to mix in water to maintain the temperature < 200C. • Rails to be cut to the required length and fastenings to be removed (only if continuous sleepers of one rail length need to be removed or where inserting new sleeper is not possible. • Break the concrete around the PSC sleepers about 5-8 cm wide and upto the RCC raft bed using tractor mounted compressor. Time required for breaking each sleeper surrounding and removal of sleeper is approx. 1hr. using two compressors. Number of compressors and blowers shall be planned as per the no. of sleepers to be dealt in the given block (In this case 12 compressors were deployed to replace 40 sleepers). 429
• Thoroughly clean the broken portion to remove loose materials, dust etc., using compressed air. • Place all the new sleeper in position and again link the track with rails and fastenings to correct alignment and level duly keeping the wooden blocks on the unbroken surface to support the rails. 2.3.6 During the block operations: • Thoroughly clean underneath the sleeper and sides of broken area with water and remove the water / moisture using compressed air and cloth. • Mix the CONBEXTRA HES/ CONBEXTRA GP2 with equal quantity of 5 - 10 mm stone chips (100%) in tubs using mechanical mixing equipment with water cement ratio of 0.18 or modified as per the weather conditions. • Pour the mixed quantity to spread evenly underneath the sleeper until the sleeper is immersed by 5 mm. Roding / trowelling is done since vibrator is not suitable. • Cement concrete mix of 1:1:2 is prepared using concrete mixture. Conplast NC is added to the mix at the rate of 1.5 liters per 50 Kg bag of cement to accelerate the initial and final setting of cement and for attaining early strength of concrete. This mix is poured into the left over area evenly. • The concrete is allowed for membrane curing (Concure WB) / normal curing. • The track will be opened for traffic after 6 hrs / 30hrs of last sleeper grouted depending on CONBEXTRA HES / CONBEXTRA GP2 was used.
430
a. Breaking in progress
b. After removal of broken sleeper
c. Before attention
d. After attention
• Description of items operated for executing the work NS 1) Breaking the damaged sleepers in the apron including breaking the apron by 80mm wide in average around the sleeper including the damaged mastic pads and removing the debris and dumping on the adjacent platform for further leading to outside the railway land to enable the new sleeper to be inserted, which will be paid separately with all contractors labour, tools, tackles, lead, lift etc., complete and as directed by the engineer-in-charge at site. NS 2) Providing conbextra GP2 and mixing with 10mm down size well graded chips and grouting underneath the sleeper at isolated locations, executed in the specified block period provided during 431
Day/Night with all contractors material labour, tools, plants, machinery, lead, lift, transportation, etc., complete and as directed by the engineer-in-charge at site. Note: 1) The work shall be executed as per the instructions of Engineer-in-charge. 2) 10 mm down size metal shall be mixed equal to the weight of Conbextra GP2(100% by weight) 3) The stone chips shall be screened, washed and shall be kept wet before using mixing with Conbextra GP2. 4) The complete quantity required for one sleeper shall be mixed simultaneously with six different mixing batches with separate mixing equipment required. 5) The complete surface area i.e. bottom and sides of the broken portion need to be cleaned using air compressor to remove the wet and loose particles completely. 6) Before grouting the surface need to be thoroughly washed and the excess water need to be removed with wet cloth. NS 3) Providing conbextra HES and mixing with 10mm down size well graded chips and grouting underneath the sleeper at isolated loactions excuted in the specified block period provided during Day/Night with all contractors material labour, tools, plants, machinery, lead, lift, transportion, etc., complete and as directed by the engineer-in-charge at site. Note: 1) The work shall be executed as per the instructions of Engineer-in-charge. 2) 10 mm down size metal shall be mixed equal to the weight of conbextra HES(100% by weight) 432
3) The stone chips shall be screened, washed and shall be kept wet before using mixing with conbextra HES. 4) The conbextra HES shall be mixed in cool water less than 20 C with 10mm down size course aggregate for a period of five minutes. 5) The complete quantity required for one sleeper shall be mixed simultaneously with six different mixing batches with separate mixing equipment required. 6) The complete surface area i.e. bottom and sides of the broken portion need to be cleaned using air compressor to remove the wet and loose particles completely. 7) Before grouting the surface need to be thoroughly washed and the excess water need to be removed with wet cloth. NS 4) Providing and laying during the specified block period cement concrete mix of 1:1:2 using 20mm nominal size aggregate duly mixing Conplast NC @1.5 Liters/Bags of cement for filling on the sides of the newly laid sleepers. over the Conbextra GP2 / HES (Separately paid) up to the top profile of the washable apron and finishing smooth with all contractors materials, labour, tools, plants, machinery, lead, lift, transport etc., complete and as directed by the Engineer-in-charge at site. 4.0 Conclusion The above method of attending to isolated broken sleepers in washable apron proven to be successful as it requires minimum traffic block as against conventional method of using ordinary Portland cement. Depending on the site conditions and availability of traffic block either Conbextra HES or Conbextra GP2 can be used. Conbextra HES is approximately 3 times costlier than Conbextra GP2. Considering the saving in valuable traffic block periods, this method of replacing the broken sleepers in the apron is proven to be economical and can be adopted for replacing isolated broken sleepers with minimum efforts. 433
BALLASTLESS TRACK PRACTICAL DIFFICULTIES IN LAYING & MAINTENACE - Kaushal Kishore, Chief Engineer (General), WCR -JN Verma, Dy.Chief Engineer (General), WCR ___________________________________________________________________
Synopsis: This paper while discussing the origin and use of ballastless track word-wide, a crisp comparative analysis of ballastless track visa-vis conventional ballasted track, gaining of momentum of ballastless track structure on metro and tunnels, design aspects of ballastless track for normal unrestricted speed, goes into the genesis of problems of concrete apron, attempts to suggest simple seven precautions to be observed while laying washable concrete apron, so as to avoid costly and time consuming repair at later stage. 1.
Introduction:
On Railways of Germany, Japan, Netherlands, the ballastless track are in use since 1972 and are in service for about 40 years with little maintenance. The % of ballast less track is increasing in construction of new lines. In Japan, it constitutes 96 % of total length of construction of new lines. Initially, the use was restricted for specific purposes such as Rapid Transport System, tunnels etc. But despite the higher initial cost of laying (about 2 times higher), the use of ballastless track is gaining momentum because of very little maintenance cost, thus proving competitive, if not economical, as compared to the conventional ballasted track. The test runs were on ballastless track were carried out successfully upto 250 kmph in 1972 itself. In fact for higher speed and high axle load, ballastless track is ideal because of inherent advantages such as little maintenance, low structure height, great lateral stiffness, easy to
435
clean, low dead weight on engineering structure, no problem due to churning of ballast particles etc. In India, use of ballastless track even after passage of more than 40 years after its inception world-wide, has remained confined to the underground rail network of metropolitan projects, tunnels and as concrete apron for platform lines (with restricted speed of 35 kmph). The use in India gained importance on after its use on KK line of SE Railways (which is for predominantly for Goods traffic), on JammuUdhampur project (tunnels) and on Konkan Railway (tunnels). This is in order to take advantage of low structure height and on ground of little maintenance it requires in future. But, hardly there is any example of use on account of higher speed and other inherent advantages of ballastless track in open areas. Now-a-days, it is being used predominantly in Metro projects, especially in case of underground tunnels. However, as concrete apron, it is being substantially used for platform lines. But due to faulty design, there have been problems of cracks in concrete, shaking of sleepers, and drainage etc even before the lapse of 5 years in service. This has been so, when there is an speed restriction on platform apron. This paper while discussing the design aspects of ballastless track for normal unrestricted speed, goes into the genesis of problems of concrete apron, attempts to suggest precautions to be observed while laying concrete apron, so as to avoid costly and time consuming repair at later stage. 2.
DIS-ADVANTAGES OF CONVENTIONAL TRACK :• The many proven advantages of conventional ballasted track are counter-balanced by great disadvantage of constant need for maintenance.
436
• For high speed and high axle load, Slab track is a substitute for ballast bed and sleepers. • Higher structure height and heavy dead load. 3.
ADVANTAGES OF BALLAST-LESS TRACK : • Lower maintenance requirement and hence higher availability. • Reduction in structure height / lower dead load on engineering structure. • Increased service life. • No problem with churning of ballast particle at high speed. • Higher lateral resistance, which allows future speed increases in combination of tilting technology. Also favorable in connection with horizontal forces and stability. • Saving in noise - reducing measures. • Greatest saving in tunnels and on bridges. • No settlement hence little maintenace. • No noise nuisance during night from tampers. • Low height (important for tunnels). • Easy to clean (stations).
4.
DIS-ADVANTAGES OF BALLASTLESS TRACK : • High cost & much time required for track laying or possession because of high degree of precision. • Level adjustment requires accurate finishing of structure or use of base plates of variable sizes. • Changes at later stage are difficult to implement. 437
• Discontinuities at subgrade point of transition (change of stiffness). • Great influence of temperature makes expansion devices more of necessity than on ballasted track. • Noise vibration damping is problematic. 5.
DESIGN CONSIDERATIONS : Points to ponder • Whether for restricted speed or for normal speed. • For tunnels or bridges or for platform lines. • Cast-in-situ or pre-cast slab. • Using normal PSC sleeper or modified PSC sleeper or with RCC blocks. • Transition with conventional track. • Design should be permanently stable & safe track bed. • Economical to manufacture and operate. • Quick and simple to install, should repair prove necessary. • Possible means particularly noise.
of
avoiding
environmental
nuisance,
• Provision of central and transverse drainage • Possibility to consider a separate joint between track slab and subgrade. • Reconstruction of smaller elements in event of repairs. • Possibility of incorporating elastic matting to reduce the noise i.e. to be designed to offer improved vibration attenuation by interposition of elastomeric layers with rigid track structure.
438
6. BASIC PRINCIPLE: Elasticity of ballast bed in slab track is obtained by inserting two elastic rubber bonded cork layers between rail & base plate and between base plate and concrete slab, and by using double springs consisting of DE clips and coil springs. 7.
TYPES OF BALLAST-LESS TRACK : • Sleeper principle based: Sleepers are cast into a concrete slab - this system uses PSC sleepers on a concrete slab with rail being supported at discrete points , just like conventional ballasted track. • Embedded Rail Structure (ERS) : involves provision of continuous support for rails by means of compound consisting of Corkelast.
8.
MOST WELL KNOWN SLAB TRACK STRUCTURES, PRESENTLY IN USE : • Rheda, Zublin & other variant (Germany), sleeper cast into
concrete slab. • Stedef, Sonneville Low Vibration (France), tunnels, metro,
rubber boot under sleeper for elasticity. • Walo (Switzerland), twin-block sleeper fitted with rubber boots. • Edilon Block Track (Netherlands), (Switzerland), mainly bridges & tunnels.
same
as
Walo
• Shinkensen slab track (Japan, S. Korea), pre-fabricated slab
track of 5m, since 1972. • IPA Slab track (Italy), same as Shinkensen. • OBB-Porr (Austria), embedded mono-block sleeper, same as
Rheda. • Embedded
Rail Structure (Netherlands), continuously supported rail system, 20 years experience, little maintenance. 439
9.
RHEDA DESIGN OF BALLASTLESS TRACK : • Designed by Prof. Dr. Ing. Eisenmann, Munich Technical University(1972). • Laid over 640 m length. • Used by 76 passenger trains per day. • Regulation speed = 160 kmph. • Test runs were carried out at speed upto 250 kmph. • Design is composed of (from bottom to top) as follows: • 150 mm thick cement reinforced bed (M-5 equivalent strength). • 200 mm problem)
layer of styroper light concrete ( to control frost
• 140 mm concrete slab, steel reinforced throughout (M-35 equivalent strength). • Concrete sleepers (spacing 600 mm apart) • Back-filling of track panels (lean concrete of M-25 equivalent
strength). 10.
PARTS OF BALLAST-LESS TRACK: • RCC base plate - pre-fabricated or poured at site, a U-shaped concrete trough. • Track Panels - comprising the rails, concrete sleepers and a reinforcement - track panels are finally concreted into the position. • A Elastomer layer - inserted between trough and RCC protective concrete layer to help protect seal. • Construction joints - provided between each trough section. 440
11. WASHABLE CONCRETE APRON: In design of washable concrete apron for platform lines, PSC sleepers are directly laid on hard concrete base and are kept in position by concrete pour all around. While constructing concrete apron, following seven points are of paramount importance: 1) Substructure: Substructure needs to be constructed as given in the Fig.1. Proper compaction of subgrade layer of murrum and good quality control of CC and RCC is essential to ensure longevity of service life of the CC apron. Longitudinal reinforcement of 12 mm dia TOR bars @ 450 mm c/c (8 bars) and cross reinforcement of 12 mm dia TOR bars @ 380 mm c/c is provided at the bottom of RCC layer. At top of the layer, grid of reinforcement of 12 mm dia TOR bars @ 340 mm c/c may be provided at both places of rail seat.
Fig. 1
441
2) Expansion Joints: There must be a provision of expansion joints at every 45 m. centre to centre in layer of RCC concrete to take care of thermal expansion. It may be an expansion gap of 12 mm in bed @ 45 m centre to centre. Gap is to be filled by polyethylene foam. 3) Double Drainage Arrangement: It must have two sets of drainage arrangement namely open drains and underground drainage network as given in Fig.2. Manholes for underground drainage must be at every 250 m. with longitudinal slope of 1 in 250. The surface drains can have summits and nadirs at every 250 m with 1 in 250 gradient as shown in fig. 2. The bottom of surface drains need to be kept in shape of half round. This will ensure required self cleansing velocity.
Fig. 2
4) Shear Keys: Proper shear key impressions needs to be left at junction of layers of CC and RCC layer as well at junction of RCC layer and second pour concrete. This will ensure proper bonding between two concrete layers and there will not be separation of two layers in service life. Shear keys are must. Brick-size wooden pieces can be embedded in the top surface of RCC concrete to leave impressions to act as shear keys. These may be provided at a random spacing of 3 m. In addition, top surface of RCC needs to be roughened for proper bonding. 442
5) Enveloping PSC sleepers: Second pour concrete (M-20 using stone aggregates of 6 to 20 mm nominal size) must envelope the sleepers from all sides except top. For this purpose, sleepers are required to be supported on 50-75 mm thick pieces either of wood or stone chips/concrete. The provision of these spacers will help in adjustment of the height and help in attaining proper RL of rail level removing differential RLs due to undulations in top level of RCC concrete. Thus perfection in RLs of rail level track can be attained. This will reduce if not eliminate the impact of moving load and consequently cracking of 2nd pour concrete.
Fig. 3 6) LWR Track structure: Track structure needs to be LWR. This is essential to attenuate the impact load of moving train. Track need to be laid as per the design rail levels using level instruments. 7) Transitions at both ends: There must be provision of transitions at both ends of platforms. This will help avoiding cracks at ends and smooth switch over of trains from ballasted to ballastless track structure.
443
These points were taken care during construction of concrete apron at platform line no. 7/8 at Bhusawal junction of Central Railway. Photographs of the concrete apron at platform line no. 7/8 at Bhusawal junction of Central Railway, taken in the month of Sept.’2012 is enclosed. The concrete apron was constructed in year 2003. As expected the concrete apron at Bhusawal is still functioning OK even after lapse of more than 10 years without need of any repairs. Thus adequate time needs to be given for quality construction concrete aprons on platforms. 12.
SPECIFICATIONS: • Polyethylene foam to specification No. RDSO/M&C/RP184/94. • Water sealant [Conforming to IS:1834-1984(Grade -B)] shall be bitumen emulsion type, to be applied all around the sleeper at periphery of pocket after sleepers are laid. • Grout - non-shrinkable grout of approved quality shall be used. • Expansion Joint - expansion gap of 12 mm in bed @ 45 m centre to centre. Gap is to be filled by polyethylene foam.
13.
PRACTICAL DIFFICULTIES: • Shaking of PSC sleepers. • Cracks around the sleeper in second pour concrete. • Centre binding condition of sleepers. • In-adequate drainage.
14.
RECOMMENDATIONS: Based on experience of various concrete aprons constructed on Indian Railways, suggestions are summarized as under: 444
• Follow design of double elastic media, one between rail and sleeper and another between sleeper and concrete slab. • Provide proper drainage arrangement, longitudinal and transverse. • Observe strict quality control for material and construction. • Pre-compress sleeper rubber pad of the track panels. • Go for design of ballastless track with unrestricted speed. • Do provide the transitions at both ends of platform apron. • Surface finishing of bottom of PSC sleepers should be done. • Provide LWR track structure. • Use foam at centre to avoid centre-binding of PSC sleepers. If these basic seven recommendations in design and construction as elaborated in Para 11 above are observed, it is expected that concrete apron will last for much longer duration without any maintenance inputs. 15.
REFERENCES: • Slab track - A competitive solution, by Dr. Coenraad Esveld (Article published in Rail International, May’1999). • Ballastless tracks for Berlin Stadtbahn by Dr. Lother Fendrich (Article published in RTR - 1(1996). • Un-conventional Track - UIC / ORE, D-87. • Central Railway Drawing No. GM(W)BB 9691/B for Washable concrete apron with PSC Sleepers. • Ballastless track on bridges - Development & Experience to date by Kurt Gerlich (Article published in RTR - 2(1995).
445
Photographs of the concrete apron at platform line no. 7/8 at Bhusawal Junction of Central Railway (Year of construction : 2003.9, Photographs taken in Sept.’2012)
CAST IRON GRILLS OVER SURFACE DRAIN
446
SURFACE DRAIN
447
PRECAST WASHABLE APRON ON RTM STATION A CASE STUDY - A.M. Kaushal, Dy. Chief Eng.(TM)Churchgate, W.Rly - Narendra Singh, ADEN /NW/ADI _____________________________________________________________
Synopsis: We all know about nuisance on the platform lines due to droppings from stopped trains. Conventional track with ballast on platform line cannot be kept clean and creates unhygienic condition along with deteriorated track condition due to slushy condition and water logging which gives rise to flies and mosquitoes and makes whole station yard area shabby and unhealthy.
Only solution to above problem is provision of washable apron. So far several methods have been tried but mostly all techniques involved traffic block of 45 to 60 days. With the enhanced traffic and limitation of PF lines it is very difficult to close a PF line and Passenger PF for such a long periods. 449
Several sanctioned work of CC apron on busy PF either could not be executed or delayed on account of demand of 45 – 60 days block. A different approach has been adopted in PF No.7 of RTM station on BCT-NDLS Rajdhani route to suit the need of future of less block period with enhanced quality control by casting RCC slabs in depot, under strict supervision. 1. Brief history of case The work of construction of washable C.C. Apron on BG Line No. 10 (PF No. 07) was initially included in LB-2006-07 and the work was proposed to be executed along with GC work by S&C. However S&C department has not executed the work and transferred the same to division after commissioning the project. Finalization of GAD and sanctioning of Detailed estimate were delayed on account of non finalization of modus operandi as after opening of section, blocking of platform line for 45-60 days was not agreed by traffic deptt. After several brain storming sessions, an innovative idea of using precast slab was conceived to save block time and detailed estimate was prepared accordingly and got sanction on 13.05.2009. Traffic block of line no. 10 PF No. 7 was taken on 14th May ’10 for 20 days but track has been handed over in 19 days i.e. on 3rd Jun’10. 2. Problem with present practices. Following methods of providing washable apron were adopted on IR in past. 1. Pile method 2. Twin block (concrete/wooden) method 3. Laying of concrete apron with PSC sleeper 4. Ballasted cum precast slab type apron 5. Monolithic CC apron RHEDA method.
450
Limitation of present practices. Sr.No.
1
2&3
4
5
3.
Method
Main limitation
Pile
a) Entire load is transferred through pile only, thus due to running of heavy traffic piles as well as concrete gets disturbed with time resulting in damage to apron. b) Block requirement is also of 45 – 50 days.
Twin block method and CC apron with PSC sleeper
a) Block duration is quite high to the tune of 45-60 days. b) Quality control on in situ concreting is very difficult due to time &space constraint. c) Due to vibration of running traffic from adjacent line, distortion in set dimension of concrete is apparent causing poor retention of track parameter.
Ballasted cum precast slab type apron
The track is ordinary ballasted track but precast slabs kept in between two PSC sleepers over ballast and joints between slab & sleeper sealed with bitumen mixture. Joint sealant get disturbed frequently due to continuous water contact and track parameters start disturbing. Track parameter attention is very difficult as it requires traffic block to remove these slabs before attention.
RHEDA
a) Cost is abnormally high. b) Design is approved only for specific project, cannot be used at all the places.
Specific features of Innovative method for CC apron
Keeping the above discussed problems in view, an innovative method of CC apron was tried on PF No.7 of Ratlam station of Ratlam Division of WR. In order to enhance the quality control while 451
concreting and to save precious block time ( 21 – 30 days), pre-cast slabs were made, curing of which was done in specially made water tanks in pre block period. Casting of precast slabs was done in depot outside the PF area keeping finishing dimension under strict tolerances and providing requisite curing by fully immersing in water tanks. After completion of curing period these slabs were launched on leveled surface having rubble soling below leveling course of quarry dust. The precast slabs were having special locking arrangement at the end to avoid any relative longitudinal movement as well as to have nearly gapless joint. All requisite longitudinal gradient as well as super elevation for the track has been given while preparing formation / sub grade for these slabs. On this bed of precast slabs, track with PSC sleeper has been laid to accurate dimension and concreting is done in between the sleeper to provide cross slope for smooth flow of waste with water. In this way the concrete which is carrying whole load of traffic has been prepared in depot to have assured optimum strength, durability as well as dimensional accuracy without wasting precious block time on account of curing of load bearing concrete. 4.
Technical details. 1.
Drawing No - CE (W)20050-DRM/3D
2.
The Design load - BGML
3.
Speed potential - Narmal speed (50 to 60 kmph).
4.
RCC – M 30 Mix design
5.
Steel Reinforcement - Fe415
6.
Anticipated life - 30 to 40 years.
452
5.
Step by step procedure:
5.1
Pre-block activities: i) Casting of specially designed RCC slab(1.65x3.15mt)of M-30 grade as per drawing enclosed in depot with highest level of quality control under strict supervision to get optimum strength as well as dimensional accuracy.
ii) Planning for proposed grade and level of track on CC apron. iii) Survey of existing track for side structure such as platform wall, drainage, water hydrants etc. iv) Working out details of existing subsoil and sub-base structure. v) Benchmarking of proposed level of track and other related structure such as sewer lines water lines electrical and signal cable subway etc. 5.2
Machinery desired 1. JCB-2 No.for 3 days 2. Hydraulic lifter – 08 tones capacity = 04 No. 3. Road roller – 01 for 02 days
453
4. Concrete Mixer (Diesel) = 05 sets for 3 days for in-situ concreting only. 5. Tractor with trolleys = 04 No.( for muck removing)
5.3
Activities during block period a. Days 01 to 05.
i)
Dismantling of existing track. Keeping rail near the track away from platform wall. Sleeper to be kept on platform away from coping with sufficient margin for moving of hydraulic lifter.
ii)
Removing of existing cushion of ballast and muck below the sleeper with the help of JCB and tractor trolleys from both ends of platform.
iii) Excavation is to be done upto desired level in reference to B.M. to accommodate rubble soling, Moorum filling, quarry dust, leveling course and precast RCC slabs, sleepers, Rails etc. iv) Consolidation of subgrade with the help of road roller. v)
Stone soling 230mm thick by hand packed Rubble.
vi) Filling and rolling with small size hand broken rubble. vii) Laying Moorum and ramming ,watering and consolidation using mechanical roller upto a ready thickness of 50mm.
b. Day 06 to 08. i)
Fixing of Precast slab one end to another on the surface leveled by quarry dust (0-06 mm) with the help of hydraulic lifter. 454
c. Day 09 to 10. i) Spreading of sleeper and linking of track with the help of hydraulic lifter. ii) Watching loose slabs and sleepers by rolling one light engine on newly linked tracks and identifying them. iii) Packing loose slabs/sleepers so demarcated iv) Filling of epoxy with fine sand in between slabs joints v) Filling of Bituminous concrete between sleeper bottom and top of slab as filler for making level surface of track if needed. d. Day 11 to 21 i) Monolithic cement concreting of 1:2:4 around and in between the sleepers with proper slope toward drain to keep cleanliness and drainage under the rail flange
ii) Rest of the days curing will be done as per norms. iii) Side drain wall as per drawing will also be made simultaneously.
455
6. Cost comparison: Cost comparison of all prevalent methods as well as proposed method is as under: Sr.No. 1
Methodology
Cost per RM of track (aprox.) excluding Rail cost Rs. 15000/-
Ballasted apron CC apron with PSC sleeper REHDA design Pre cast CC apron
2 3 4
Rs. 15500/Rs. 45000/Rs. 15000/-
It can be seen from above comparison that initial cost is on lower side among all prevalent methods. Moreover due to higher level of dimensional accuracy no relative movement between sleeper and base concrete slab would occur and it could be presumed that no maintenance cost will be incurred in future.
7. Conclusion : i)
Better drainage facilities with proper and timely cleaning by water jet.
ii)
Zero maintenance and uniform grade as desired in yards.
iii)
Execution of work in less time frame suiting to the enhanced traffic need.
iv)
Stability of track parameters.
v)
Most economic design among available methodology.
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NAGPUR RRI COMMISSIONING - A PLEASANT EXPERIENCE - Brijesh Dixit, Divisional Railway Manager, Central Railway
Works of commissioning of new RRIs on IR along with accompanying yard remodeling have lately been very challenging. Not only the experiences of traffic blocks have been traumatic, post commissioning failures have caused even more distress. In the backdrop of this, trouble free commissioning of giant RRI at Nagpur (C.Rly.) critically situated at the junction of North-South & East-West corridors of IR without NI working and without any post commissioning hiccups, creating many firsts in the process, has been a very pleasant experience. This is how it could be done: Old Nagpur RRI commissioned on 20th Dec., 1979 having outlived its life, needed to be replaced. At the same time yard remodeling was required to remove some non-standard Diamond Crossings to improve the yard layout from safety point of view. One of them was D-16 laid in 1948 but was lately restricted for Passenger Train movements. This opportunity was also being used to streamline Goods train interchange with SEC Railway due to continuous rise in movement of coal and other commodities from mineral rich East to consumption points of Western India. Some Mechanical lever frames too were to be done away with. All this entailed additional Signaled movements, increasing the number of routes in RRI from 369 to 533, thus making it the largest RRI on Central Railway and one of the biggest on IR. Obviously magnitude of work involved was humongous, execution of which involved severe implications for both Passenger and Goods traffic through yard which could be ill offended at this crucial junction where virtually whole India as also its goods crosses from North-South & East-West.
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The inception
OLD PANEL
VIEW OF YARD
RRI work was sanctioned in 2004-05, while work of yard remodeling was sanctioned 2007-08. Indoor work of RRI was entrusted M/s. SIEMENS in MAY-2008. Outdoor work involving difficult terrain and heavy train movements could be awarded in August 2009 on fourth invitation of tender. Work physically started in September 2009. First relay rack out of 90 numbers was erected on 2nd September 2009 and the first cable out of 784 Kms. of outdoor was laid on 20th November 2009. Indoor
VIEW OF RELAY ROOM
VIEW OF CT RACK
Indoor work involved: • Erection of 90 relay racks • 804 tag blocks on IDF 458
• Pre-wiring of nearly 1.5 lac wires. • Jumpering of 55000 circuit wires. • 10,000 nos. Relays (approx). • 13 Km.,13 Km. & 8 Km. of 40, 60 & 24 core cable respectively. • Operating panel comprising 15x50 dominos and indication panel comprising of 30x100 dominos. • Wiring of 1400 fuse alarm units with 100% back up. • 160 HMUs and nearly 3200 digital data logger inputs along with 32 analogue units. • Power schematic was based on study of power schematic of Kalyan, Igatpuri and NDLS RRI. Taking best features from them, power scheme was finalised with LT panel comprising of auto change-over unit while supply to discrete power equipments from LT panel was done through fuse indication boxes with parallel, path from programme switch to the power equipments. • For signals 10 KVA UPS was proposed to ensure reliability of signals in case of OHE tripping.
Outdoor
FUSE ALARM UNIT
L.T. PANEL 459
Outdoor work involved • 784 Kms of cable laying • Erection of 116 location boxes and 50 half location boxes along with termination of laid cables in these boxes involving 80,000 ARA terminations. • Track crossing - 500 • Drain crossings - 557 Terminated in 15 C.T. racks • Platform cutting and cable crossing across platform lines and berthing tracks with minimum inconvenience to public was a major challenge which was successfully met, by doing platform work in late nights and during the TELANGANA bandh when many trains were diverted and cancelled. • Erection of 71 signals and replacement of 110 point machines.
CABLE TRENCH
Yard remodelling work Yard remodelling work involved • Removal of Two Diamond Crossings • Removal of one Scissors cross over 460
• Removal of two other cross overs • Insertion of six new cross overs • Insertion of two new turn outs • Slewing of 500 mts. of track & OHE by upto 2 mts. to new location. • Shifting of 23 masts of OHE. Principal Obstacles & Their Resolution: • Fund crunch in 2010-2011. • Changes in ESP & IP by shifting of crossover 161 by 300 m towards Itarsi. • Terminal status for platform 4 to 7 of NGP yard and legality of many existing movements became a critical issue for CRS sanction. • Derailment of a passenger train in October 2010 led to some re-appropriation of funds to this work by end of 2010 • The issue of existing movements for shunting in face of approaching train were resolved under SR 5.16.1 Testing The panel through for NGP after incorporating all the alteration needed for retaining existing traffic facilities and shifting of crossover 161 was done in July 2011. It was followed by rigorous testing in form of function test in August 2011, break test in September 2011 and square sheet testing in October 2011. Joint cable megger with open line was done in September-October 2011 while joint panel testing was done with open line in November 2011. With all mandatory testing being completed by end of November 2011, NGP RRI had reached the launching stage. 461
VIEW OF PANEL DURING TESTING
Transition Trauma Switching over from existing RRI to New RRI was a mammoth work which involved shifting of indoor as well as outdoor work to the new panel. Conventionally RRI works of this magnitude were done in N.I. of 5 to 6 days. As per the initial estimates of traffic blocks for this work goods traffic would have been totally paralysed for two weeks and cancellation/short termination/detention of M/E trains would also have been frighteningly high. No wonder traffic block planning for commissioning kept hanging for over 1 ½ years. To keep traffic repercussions to bare minimum and to go for a phase wise, gear wise transition of signaling gears from existing to new RRI. This is how it could be done:
a)
Points:
All the existing points that were retained in New NGP RRI (88 Nos.) were brought on new cable to new CT rack and were patched to old CT rack so that they continued to work on existing circuits. This transition of points involved replacement of main cable, tail cable, point machines and ground connections was done in preparatory DCN. Eight points which were in mechanical yard were 462
tested by crank handling and machine was electrically tested by clamping of slide. Remaining points were part of yard remodeling and were done in shadow of the Engg. block in yard remodeling.
PATCHING FOR POINT
b)
Track circuits
Out of existing 111 track circuits working on DRS Track relays which were inside the relay room, physical location of 92 was to remain same in New RRI. This factor was utilized and these 92 track circuits were charged with their TR (QTA2) in location boxes and TPR (QSPA1) in old relay room. The circuit of TPR on new bus-bar was first brought to new CT rack from site and then patched to old CT rack to pick up the QSPA1 TPRs. The pick up contact of these TPRs was used to pick up the existing TPRs. Also 17 new track circuits were picked up in advance. Remaining 30 track circuits which either involved yard remodeling or involved alteration in existing circuits were picked up during the yard remodeling block work by Engg. To ensure that train movements are not affected during picking up of these remaining track circuits, Calling on signals were used for the routes involving these track circuits. 463
c) Signals Out of 71 signals in NGP RRI 65 were stop signals. 13 out of these stop signals were either at location of existing signals or were located such that they infringed the visibility of existing signal. These 13 signals were made functional in the preparatory work by replacing existing signal group in old RRI by LED signal group and patching these 13 signals between new and old CT rack was done as in case of track circuits and point. Remaining 52 signals were tested from new panel to site with help of mock simulation of point and track circuits. Thus the integrity and correspondence of these 52 signals were checked in advance without any track repercussions. Commissioning Conundrum: On completion of preparatory work, 88 point machines 109 track circuits and 13 signals were on new cable working on old circuit. Similarly, the existing slots from AJNI (27 in Nos.) were shifted to new cable and patched between two new CT rack. Remaining 12 new slots between AQ & NGP RRI were also tested end to end. Remaining 30 track circuits, 22 points and 52 signals were to be charged and shifted during the yard remodeling and four hours traffic block. Though RRI & Remodeling work was progressing, modalities of the commissioning Blocks were not getting finalized owing to their frightening implication. Thus, the commissioning got postponed several times. The bullet was bitten in the end, and in a meeting at the Rly. Board involving both C.Rly. & SEC Rly. it was proposed to carry out yard remodeling in 24 Hr. block of traffic between C.Rly. & SEC Rly. followed by Four Hrs. of total block of Nagpur Goods & Passenger yard in all directions. This was accepted by C. Rly. & Nagpur Division as a challenge. Mobilization of S&T, Engg. and Electrical staff, Supervisors and Officers from both Open Line & Construction was done across C.Rly. for this purpose. However, with pre-monsoon showers drenching Nagpur by 2nd week of June ’12, execution was a major challenge at this point of time. 464
The Final Countdown Track and OHE works were done in such a way that • As per DCN Kalumna line was to be closed for four hours while Itwari line was to remain closed till the commissioning. Reception from Itarsi side was done on Calling on signals while other train movements were on main signals or Calling on signal in case of non-availability of track circuits. • To have minimum repercussions 65 track circuits were picked up in parallel so that maximum signaled moves were possible. Traffic blocks were planned from 12 hrs to 16 hrs on 13/06/2012 was rescheduled to 1.00 hr to 5.00 hrs on 13/06/2012, due to the speedy execution of the yard remodeling work. The execution of work of such a major RRI on a cloudy night was a challenge but adequate lighting arrangement was made available for night hours. But, due to train movements, the final block was permitted around 4.15 hrs on 13/06/2012. By that time all the track circuits were charged and all mechanical points (8 Nos.) were converted to electrical points from new panel. Also, all points of yard remodeling were brought to new panel. At the start of the block all points that were patched between new CT rack and old CT rack were brought to new circuits by removal
DRM IN PANEL ROOM AFTER COMMISSIONING
STAFF CELEBRATING THE COMMISSIONING 465
of patch at new CT rack. This was done within first half hour of the traffic block. Within next two hours, all main signals and slots for all the routes were tested from new panel and final reconnection of NGP RRI was given at 06.45 hrs on 13/06/2012. With this was commissioned the largest RRI of C.RLY in a shortest duration of traffic block.
Conclusion Commissioning of some of the RRIs on IR in the recent past has been done by Phase working followed by Traffic Blocks instead of conventional method of long duration N.I.s. Surat RRI in W.Rly. is the case in point. Earlier Viramgam RRI was done with short N.I period followed by traffic block. However, experience of Patna RRI proved very frightening. Way back in 1999 Delhi RRI (1124 Routes) was completed in 48 Hrs. duration. In this back drop the following were the unique features of Nagpur RRI (533 Routes) Completed without N.I. in 2½ Hrs. of Traffic Block possibly the shortest so far: •
For first time use of Calling on Signals was made to pick up track circuits without affecting signaled movement of trains. Use of Calling on signal for picking up track circuit along with using parallel track circuits in advance of commissioning can be replicated in major yards where they are avoidable.
•
Gear wise transition from old to new RRI. First points, then track circuits and signals were shifted on new cable and patched with old panel during the preparatory stage without any failure/detention.
•
785 Kms. of new cable was laid in addition to 400 Kms. of old cable underneath it, without any damage.
466
•
Post commissioning, Panel stabilized in 24 Hrs. with negligible failure even subsequently.
•
Pre-recorded message about the block and possible affect on train running on NTE No.139 was yet another first of this RRI which received good appreciation from users.
•
Traffic blocks for commissioning were executed in Mission Mode with publication of a Mission Booklet, imparting Mission Training, opening Mission Centre etc. to make it possible to accomplish the Mission RRI.
However, establishing the fact that N.I. working can be avoided fully in such works has been the biggest achievement.
467
CRITICAL ANALYSIS OF PERFORMANCE OF VARIOUS LINING METHODS AVAILABLE WITH MACHINE TAMPING N. C. Sharda, Dean, IRICEN/Pune Manoj Arora, Sr. Prof./Track-1, IRICEN/Pune Pawan Patil, Dy Chief Engineer/TM, Bhusawal, C.R D. V. B. Rao, Assistant Divisional Engineer/TM, Bhusawal, C.R __________________________________________________________________________
Synopsys: All the tamping machines available in our country provide two methods of lining i.e. 3 point lining method and 4 point lining method. In both the methods smoothening as well as design mode tamping can be done. The quality of parameters achieved by these methods are variable. It is found that the improvement achieved by 3 point lining design mode is much superior to other methods of lining. Various analysis have shown that the improvement achieved by 3 point lining design mode is almost 1.8 to 2.0 times better than 4 point lining design mode. So by a little extra effort by field staff to operate 3 point lining method may lead to major improvement in the alignment on curves. 1.0 Introduction: On Indian Railways, we have experience of working of track machines for more than 30 years. By now all the UT and UNOMATIC machines have been scrapped. In most of the Railways CSM and Tamping Express (09-3X) are being utilised for maintenance tamping, where as DUOMATIC are being utilized as work site tamper following BCM or relaying machines. Track parameters have shown trend of improvement over the years. The incidences of derailment on main line on account of track parameter have reduced drastically. However with the increase in traffic (both passenger and goods) the availability of block has gone down. The maintenance 469
corridor have been reduced on account of introduction of new trains. Hence the output of every machine may reduce in future. The availability of gangs for manual attention of track has also reduced because of vacancies in the gang. So there is a need to achieve better track parameters at the time of maintenance tamping to reduce requirement of intermittent tamping. As per Railway Board instructions, all the available tamping machines should be deployed in design mode. The implementation of design mode not only ensures that the track is restored to designed profile after tamping but it also promotes removal of permanent defects in alignment and level. However during various seminars at higher level as well as integrated courses in which AEN participate, it has been brought out that progress of implementation of design mode is at very low level, which is the reason for average quality of track after tamping.
470
2.0 Systems of lining in tamping machine: Two systems of lining are available in the tamping machines working in our country a) 3 point lining method. b) 4 point lining method. In both the methods, design mode as well as smoothening mode of lining is possible. In the absence of data for design slew, smoothening mode is resorted to in the field. The 3 point lining method is capable of producing better geometry because geometry is required to be fed while using this method. The 4 point lining method mostly compensates the existing curve. Hence use of 3 point lining method in design mode is likely to produce better result. However in case of smoothening mode, some defects are likely to remain unattended in the track, which is 1/3rd of the existing track defects in case of 3 point lining method and 1/6th of the existing track defects in case of 4 point lining method. Hence, while working with smoothening mode, superiority of 3 point lining method is compromised. However in case of design mode 3 point lining method will certainly provide better track geometry. In this paper an attempt has been made to objectively analyse the result of curves attended by three different methods i.e. 4 point smoothening lining, 4 point design lining and 3 point design lining. The quality of alignment achieved for various methods have been compared statistically. It has been found that result achieved by 3 point design mode lining is much better than the other methods. 2.1 Four point lining method: At present, at most of the places, 4 point lining method is utilized in smoothening or design mode. For operation of machine in design mode of lining, the design slews are required to be calculated by actually measuring versines of existing curve and with the help of software for realignment of curve, the slews to be fed in the tamping machine are calculated. These slews 471
are required to be interpolated for every 1.2 meter or alternate sleepers and written on the top of the sleepers, which are fed in the machine by the operator sitting in the front cabin. In spite of working in the design mode most of us must have experienced that with the present practice of working with 4 point lining method, the versine in the central circular portion may be improved to some extent but the improvement in the transition portion is normally below satisfaction level. It is also seen that at the ends of curve, S curve is formed which causes rough running. This inferior performance can be attributed to one more concept which is required to be followed on transition curve. The concept of 4 point lining is applicable directly on circular curve, but, for its application on transition curve, a correction called “transition correction” is to be applied. While entering from straight to transition curve, the machine is changed from 3 point lining method to 4 point lining method when D (i.e. front trolley) reaches to tangent point. As the D moves on transition curve, the A (rear trolley), B (measuring trolley) and C (lining trolley) are still moving on straight. So this will lead to extension of curve away from tangent point towards straight portion. This will also cause formation of S curve. Transition correction is required to be applied on both the transitions. While entering in to transition curve from straight track, this correlation has to be applied outward, but while entering in to transition curve from circular curve it is to be applied inward. The pattern of application of the transition correlation is given below. CORRECTION OUTWARD
CORRECTION INWARD
20M
Vm
20M STRAIG
20M Vm
20M
TRANSITION CIRCULAR Fig. 1: Pattern of application of transition correction.
TRANSITION
472
STRAIGHT
The value Vm can be picked up from the table available in the catalogue of machine. The pattern of increase or decrease of Vm value over 20m length can also be read from the table available in the machine. Application of transition correction ensures that no distortion of transition curve takes place because of use of 4 point lining method on transition. This correction is required to be applied irrespective of whether the machine is working on smoothening mode or design mode. This very important aspect is being ignored in field, which is leading to distortion of transition curve. 2.2 Three point lining method: This method utilises only 3 trolleys and one transducer of lining system. The versine, to be achieved by tamping are required to be calculated and fed in versine potentiometer available in front cabin. This method is also called “geometry method”. The designed versines on transition and central circular curve are achieved accurately by this method. However the error reduction ratio for this method is only 3. Hence, while working in smoothening mode, this method is inferior to 4 point lining method which has error reduction ratio of 6. But by working with design mode in 3 point lining method, best quality of track geometry may be obtained. In order to understand the difference in the quality of track geometry obtained by 3 point lining method (design mode) and 4 point lining method (Smoothening and Design mode), a study was undertaken. Different curves were tamped separately by using one of the methods i.e. 4 point lining smoothening/ 4 point lining design mode/ 3 point lining design mode and the results obtained were compared. In order to compare the results objectively, versine of curves were taken on 20m chord separately before and after tamping.
473
The average results were compared by two different methodologies, which are explained in the following paragraph. 3.0 Analysis of results of tamping: Following methodologies were utilised for comparison of results objectively. 3.1 Improvements in terms of number of stations showing variation of versine between consecutive stations beyond certain threshold value: For smooth running of rolling stock over curves, station to station variation of versine should be a small value. In order to ensure very high quality of track, a relatively smaller versine variation is expected in central circular portion immediately after tamping. Hence in circular portion, the locations where station to station variation of versine was more than 5mm were marked for study. On the transition portion, a in built variation of versine between consecutive station does exist, hence a separate norm was fixed to identify the stations not showing very good alignment. For transition curve stations where variation in versine between consecutive stations was more than designed variation +3mm were marked for study. Number of stations in a curve showing variation more than threshold value discussed above (including circular and transition curve) were marked as peak and counted before tamping for a curve. Curves tamped by a particular method i.e. 4 point lining smoothening mode/ 4 point lining design mode/ 3 point lining design mode were grouped separately for comparison of results. For all these curves versine were measured after tamping also and the stations showing variation more than threshold value decided were marked as peak for analysis. The curves tamped with one method were grouped together and their results were compiled.
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The summary of this evaluation have been shown in a tabular form:
Method of lining
4 point lining smoothening mode. 4 point lining design mode 3 point lining design mode.
% % No. of peaks in reduction reduction Transition in number in number of peaks in of peaks in Before After Before After tamping tamping full curve tamping tamping Transition by tamping by tamping No. of peaks in full curve
35
20
43%
16
12
25%
91
42
54%
39
25
36%
38
8
79%
23
6
74%
It can be seen that the reduction of number of stations showing variations in versine above predefined value is highest in case of 3 point lining with design mode, followed by 4 point lining design mode and 4 point lining smoothening mode. There is a vast difference in terms of % reduction in number of peaks. It is also seen that with 4 point lining method the improvement in terms of reduction of peaks in full curve is approximately 43% to 54% where as for 3 point lining method in design mode it is 79%. This difference is more clearly visible in case of transition curves. In case of 4 point lining smoothening method reduction in number of peaks on transition curve was only 25%. The same figure was 36% for 4 point lining design mode and 74% for 3 point design mode. Hence the quality of correction of transition is much superior in case of 3 point design mode, as compared to other two methods. It is found that the quality of performance in 3 point lining design mode is very consistent in circular curve as well as transition portion.
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It is also seen that for few curves, transition curves deteriorated when attended by 4 point lining smoothening mode. While working with 4 point lining design mode also on sharp curve, almost no improvement or slight deterioration was found in transition portion. However, while working with 3 point lining design mode the performance was found satisfactory for different degree of curve. Hence it can be concluded that 3 point lining with design mode provides the best curve including transition curves. 3.2 Improvement in terms of reduction in standard deviation of versines in curve: Although the above methodology of counting peaks above certain threshold value, provides abundant proof of superiority of performance of 3 point lining design mode over other methods. But this methodology does not clarify the smoothening achieved at the locations where the stations are not showing versine variation more than threshold value discussed in Para 3.1. In order to establish this, another analysis was done. For this purposes, analysis of improvement in standard deviation value of versine of all the stations was done separately for central circular curve as well as for transition portion. The same analysis was done for all the curves before and after tamping. It was considered that the reduction in the value of standard deviation of versine indicates the improvement in the smoothness of the curves including those cases, where variation at consecutive station may not exceed the threshold value. However the standard deviation value for transition curve is likely to be higher than circular portion because of designed variation of the versine in the transition. Because of the same fact, standard deviation in the transition portion will remain higher even after tamping. However, surprisingly at many curves standard deviation in the central circular portion was found to be more than transition portion may be because of bad maintenance of curve.
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The results of this evaluation have shown in table given below:
Method of lining
4 point lining smoothening mode 4 point lining design mode 3 point lining design mode
% Average standard deviation of versines reduction in central circular of standard deviation portion of versines in central circular portion by Before After tamping tamping tamping
Average standard deviation of versines in transition portion
Before tamping
After tamping
% reduction in standard deviation of versines in transition portion by tamping
3.41
2.66
22%
3.58
3.19
10.9%
6.53
3.76
42.4%
5.59
3.78
32.4%
5.05
1.88
62%
5.66
2.36
58.3%
This table also shows the same trend of improvement in terms of uniformity of versines in circular curve as well as in transition curve. The improvements were very high in 3 point lining design mode as compared to other methods. The %age reduction in standard deviation of versines achieved by 3 point design mode is almost thrice as compared to 4 point smoothening mode and 1.5 times to that of 4 point design mode in case of central circular portion. The difference in performance of various methods of lining is even more prominent on transition portion. On transition, improvement achieved in terms of % reduction of standard deviation by 3 point lining design mode is 5.5 times better than 4 point lining smoothening mode where as, it is 1.8 times better than 4 point lining design mode.
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4.0 Inference of analysis: Both the analysis done above clearly establish that with 3 point design mode, the improvement achieved in central circular as well as transition curve is much superior as compared to performance of 4 point smoothening or design mode. 5.0 Conclusion 5.1 It is found that there is a resistance in the P. Way staff against using 3 point lining method. Normally P. way staff is afraid of using 3 point lining under fear of very high slews. Probably people might have attempted 3 point lining method in past without knowledge, which could have caused heavy slew. But such a fear is not correct. In fact the amount of slew can be reduced by selecting proper software for realignment of curve. ALC software available on few old tamping machine and most of new machines does provide the facility to control slew. In the present study, for the curves attended by ALC method, the slew was limited to 30mm. If higher amount of slew was permitted (let us say 50mm), the degree of improvement achieved by 3 point design mode could have been more. 5.2 It is also feared that the 3 point lining method will attempt to provide uniform versine throughout the curve which may cause curve going out of the formation. Such a fear is also not correct. In Central Railway as well as few other railways, the machines having ALC are being utilized with 3 point lining method but at none of such place such eventuality took place. 5.3 At the same time, it should also be remembered that the error reduction ratio for 3 point lining method is 3, where as for 4 point lining method it is 6. Hence in case machine is used in smoothening mode, the superiority of 3 point method erodes. Hence good curve can be obtained only by 3 point lining design mode. 5.4 In case curves are attended by 4 point lining method, transition correction must be applied to avoid formation of ‘S’ curve.
478
5.5 At IRICEN it was found that most of the officers coming for training do not have the knowledge about how to calculate versine on transition for 3 point lining method. After proper training in 3 point lining method, they are better equipped to handle 3 point lining method. Software developed by Eastern Railway provides calculation of the versines for transition curve, hence now there should not be fear of using 3 point lining method. With very little extra effort by P. Way staff results achieved by tamping can be improved drastically. It may also be noted that many of developed railways are procuring machines without 4 point lining system, which may help to reduce cost of procurement also.
479
IMPROVING RELIABILTY OF IN-SERVICE RAILS ALIGNMENT RECTIFICATION & RETENTION ON CHANNEL SLEEPERS ON BRIDGES - P.V.N.Naidu, Principal/ DCETC/BZA - G.Kiran Babu, Instructor/DCETC/BZA
_______________________________________________________ 1.0
Introduction
Maintenance of track on bridges was never a simple task for P. Way Engineers. The alignment of track on Steel channel sleeper on bridges is getting disturbed frequently due to dynamic loads. There are various reasons for the disturbance of alignment on steel channel sleeper track on bridges. Lateral forces are induced on the rail due to defective alignment of track which will in turn lead to development of undesired stress in the rail. Whenever lateral forces are more it will lead to development of kinks and abnormal wear requiring pre-mature renewals. 1.1
Measurement of alignment defects on Bridges.
Many methods for measurement of alignments on track were tried with instruments like theodalite, total stations etc. The solutions given with these equipment involved heavy slews and their ability of sighting objects beyond 300 mts is not reliable. It was found that the track on the bridges was never a straight line. The net existing versine was always found indicating a curvature of big radius on bridges. The string lining method (which was used for rectification of alignment defects in curves) was tried for rectification of alignment defects. The string lining method is having the flexibility of re - alignment with multiple options of restricted slews. It was very successful in giving solutions to alignment defects on track on bridges. 481
The chord adopted for measuring the versine on bridges was 10 mts overlapping chord at an interval of 5 mts. The following Table shows the solution used for rectifying the alignment defect on the bridge 594. Re-alignment on bridge 594 dn by string lining method Station 1st 2nd No. Ve Vp vp-ve SUM SUM slew -3 -2 -2 0 0 -2 -14 -6 8 8 0 0 -1 3 -4 -7 1 8 16 0 5 -3 -8 -7 9 18 1 1 3 2 -5 2 4 2 -6 0 6 1 -3 -6 3 -2 -4 -2 -1 -2 -4 4 -6 -3 3 2 -3 -6 5 -5 -3 2 4 -1 -2 6 9 3 -6 -2 3 6 7 -5 -3 2 0 1 2 8 2 2 0 0 1 2 9 0 -2 -2 -2 1 2 10 -3 7 5 -1 -2 -10 11 3 0 5 4 8 3 12 -2 -14 -9 9 18 12 13 3 16 7 0 0 -13 14 -2 -3.3 -1.3 5.7 7 14 15 9 0 -9 -3.3 12.7 25.4 16 2 0 -2 -5.3 9.4 18.8 17 -2 0 2 -3.3 4.1 8.2 18 2 0 -2 -5.3 0.8 1.6 19 -7 0 7 1.7 -4.5 -9 20 -2 0 2 3.7 -2.8 -5.6 482
Station No. 22 23 24 25 26 +1 +2 +3
Ve Vp vp-ve -3 0.04 3.04 6 0 -6 8 0 -8 3 0 -3 0 20 -20 14 -0.04 -14.04 -8 -3.7 4.3 0 0 0 -28 -28
1st SUM 6.74 0.74 -7.26 -10.26 9.74 -4.3 0 0
2nd SUM 4.6 11.34 12.08 4.82 -5.44 4.3 0 0
slew 9.2 22.68 24.16 9.64 -10.88 8.6 0 0
If the final versines are not satisfactory with the restricted slew of 20-30 mm then a two pronged system to be adopted to rectify the alignment on bridges. First the alignment to be measured with a chord length of 2 x girder lengths of the bridge. The stations should be the junction points of girders. After calculation of the slews the slew points will be the girder junctions. The slews are restricted to 20 mm at girder junctions. After the correction of alignment on 2 X girder length chord. Again the track on girder bridges is measured with 10 mts chord length with 5 mts interval and corrected by slewing the track. By adopting this method it can be ensured that the eccentricity of track on girder is maintained at the level of 20 mm 1.2
Rectification of alignment of Track on Bridges a new approach
The present method of rectification of alignment defects is with simplex track jack. The minimum slew that can be rectified with simple jacks is in multiples of 15 mm. The application of track jack needs speed restriction and the jack will be infringing the trains. The main constraint will be the jack has to be removed when
483
ever the train passes and it is to be re-fixed. The method is very cumbersome and track safety is involved. A lining screw jack was fabricated from the scrap material of SE/PWAY/BPP office to rectify the alignment defects on steel channel sleeper track.
This screw jack will be having a jaw on each end of the screw .The central part will be having a screw arrangement such that the rotation in the clock wise direction will reduce the overall length of the jack arrangement and the rotation in anti clock wise direction will increase the overall length of the jack arrangement. One jaw will be fixed to the girder on direction to which the track is to be slewed. The other jaw will be fixed to the rail. When the central part screw is tightened by rotating in clock wise direction the length is reduced and a lateral force is developed and track is slewed in the direction where the jaw is fixed to the girder. If the track is to be slewed to other direction then just by reversal of the arrangement will be sufficient. 484
This system is having several advantages to the existing system of lining the track on bridges with track jack. This is light in weight and it can be handled with three persons. The procedure is so simple that the rectification in alignment on Lining of Track by Single Man
bridge can be carried out with six men and at least 8 to 10 locations can be attended with in one day. The alignment rectification can be carried out up to 1mm accuracy. The arrangement is non infringing and hence it can be left in the working position while passing the train this saves lot of time and the work can be started from the location where it was stopped for passing the train. Earlier the expertise of bridge staff was taken for carrying out the alignment rectification work on bridges. But with the present arrangement P.Way staff were able to attend the rectification of 485
alignment. The present arrangement was successfully in use with the all above said advantages by SE/P.Way/CLX, SE/PWAY/BPP, SE/pway/TEL, SE/PWAY/OGL The preliminary estimate to fabricate a customized lining screw jack may be Rs 12000 to 14000 1.3
Retention of alignment after rectification
Retention of alignment on the bridges after re-alignment has been a big task after rectification. The steel channel sleepers are fixed to the girders of bridges with hook bolts in vertical direction. Rectangular holes are provided in the steel channel sleepers for providing the hook bolt at the bottom channel sleeper and a circular hole at the top. The lower lip of the hook bolt will be holding the girder and upper part of the hook bolt is provided with nut. The channel sleeper is held in position in vertical and lateral direction with the hook bolt 1.3.1
Problem with Hook Bolt
The alignment of track on steel channel sleeper bridges is frequently disturbed due to the inability of the hook bolts to hold the steel channel sleepers in lateral direction. As the hook bolts are provided in the oblong slot of channel sleeper at the bottom and a play of around mm is available at the bottom of the channel sleeper. A lot of play is available between bolt and steel channel sleeper slot, hence the hook bolts are unable to restrain the lateral forces coming on to the sleepers properly because the lateral force on the channel sleeper is exerted at an angle of 90 degrees to the holding direction. 1.3.2 Introduction Alignment Retainers
of
The alignment retainers are made up of two bars of 25mm dia of length around 70 to 75cm with a 486
hook arrangement on one side and threading arrangement with nut on the other side. The hook side of the bar is anchored to the girder and threaded side is passed through an angle of 65 X 65 X 10 (the initial designs was with 65x65x6 but later on during last two years of experience it was found that 65x65x10 are holding better). The angle will be holding the steel channel sleeper at the top of the steel channel sleeper. When the nut is tightened on the angle the steel channel sleeper will be locked in lateral and vertical direction. As the direction of holding the steel channel sleeper is at an angle from 30 degrees to 60 degrees to the direction of the lateral and vertical force. This arrangement will be holding the steel channel sleeper in both vertical, lateral direction and longitudinal direction. The 25mm dia bars are provided on both the sides of the channel sleeper in longitudinal and lateral direction. This arrangement restricts the movement of steel channel sleepers in all the directions and disturbances to alignment and surfacing will become nil. The retainer arrangement is provided at every 4 th or 5 th sleeper. Complete arrangement of Aliment Retainers
487
The entire set per sleeper costs around Rs.4500/-. This arrangement was trail on bridge nos 676 DN, 608 UP,594 UP, 594 DN between in ADEN/BPP Section in Sr DEN/C/BZA, Sr DEN/S/BZA of Vijayawada division , Sr DEN north sub-division of SC Division. The arrangement was found to be successful and no disturbance to the track was observed after providing the above arrangement. And the design is under trail in Eco RLY and W, RLY also. In Eco Rly this arrangement was provided on the curved track on bridges. 1.3.3
Advantages of New System
•
Retains alignment of track in lateral direction of track
•
This arrangement not only holds alignment but also holds sleeper in vertical direction
•
Reduction in maintenance of channel sleeper track on bridges
•
During maintenance if any alignment defect arises it can be rectified up 10 mm by the alignment retainer
1.4
Topi Nuts for T –Head Bolts and Hook Bolts for Reduction of Oscillations and Improving Maintenance
The steel channel sleepers are fitted with 10 sets of bolts and nuts for each sleeper. The T head bolts connected with the running 488
rails are subjected heavy vibrations these bolts due to dynamic loads of moving trains. The problem of loosening of nuts is leading to excessive play between the fittings .The play in fittings is further leading to distortion of track parameters and leading to the imposition of speed restrictions on the girder bridges. The bolts and nuts which are subjected to dynamic conditions are prone for loosing. In the year 2006 the provision of castle nuts was introduced in S C Rly in ADEN/KRNT sub division of HYD division of S C Rly. The castle nut arrangement for T head bolts and Hook bolts was successful with some limitations. The castle nut arrangement with cotter pin doesn’t have the provision for providing the split pin at a location where the specific torque is arrived. They have to be rotated upto a maximum of 1/12th pitch to match with the hole of the bolt ie compressing/slackening the rubber pad by 0.2 mm. This will lead to excessive tightening or slacking of nut bolt arrangement. The rubber pad takes a load of 15 tons for a compression of 0.15 mm. If rubber pad is compressed by 0.2 mm for matching the hole of bolt with the groove of nut .The elasticity in the rubber pad ceases. When axle loads pass over the rail the rubber pads are crushed and stresses in the rail increase In addition to the above problem the nuts of the T - head bolts were to be removed and grooves are to be made. While making grooves to the galvanized nuts the galvanization was lost and signs of corrosion were seen. In order to completely eliminate the problem TOPI NUTS were introduced. The TOPI NUT is made up of molded GFN material. This will have five parts the bottom part made up of cylindrical shape. The bottom part of the topi nut will be holding the nut in position. Slots are provided in the vertical faces of cylinder portion so that cotter pin can pass through the topi nut cylindrical portion at any stage of bolt hole. The cotter pin passing through the bolt hole will hold the nut in position and prevent it from rotating. This arrangement provides the 489
anti rotation arrangement at the location where the specific torque is arrived. This will also provide a cover over the bolt nut arrangement from being damaged by night soil and rain and prevent corrosion of bolt nut arrangement. 1.4.1
Advantages of the System
The arrangement servers the purpose of 1 anti rotation 2Ability to provide locking arrangement for a fixed torque The crushing of rubber pads is eliminated and life of rubber pads is increased The corrosion of fittings due to exposure of nuts to rain and night soil is eliminated The topi nuts can be provided on the existing fittings easily. No assembly of the existing fitting to be removed for providing the topi nut. No grooving of the existing nut is required as it is done now for providing the split pin through the nut. The failure of galvanization and corrosion of nuts of channel sleepers due to slotting of the already galvanization nut is avoided. 490
Topi are provided over the existing nut in as it is condition with out further rotating the nut for matching the hole of bolt with slot ABSTRACT Channel sleepers have given a good solution to wooden sleepers on girder bridges. But due to high number of fittings on channel sleepers the maintenance has increased. The gauge retention on the channel sleepers is better than that on the wooden sleepers. But alignment retention on the girder bridges laid with steel channel sleepers was a serious problem for in service Rails. Rails laid on the Channel sleepers may require pre-mature renewals. Running on the channel sleeper bridges was always a serious problem. At times it was also thought to replace the channel sleepers with Composite sleepers or FRP sleepers.
An attempt was made in this paper for showing the solutions to channel sleeper bridges for measuring, rectification and retention of alignment on girder bridges with practical solutions which are time tested in SCR & ECoR.
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POLYMERS, RAIL CORROSION CONTROL BY FIBRES & FIBRES IN CONCRETE M. Suyambulingam, C.E.
_______________________________________________________ Synopsis: Polymers are used for imparting certain special properties to concrete, while fibres dispersed in concrete increase its fatigue strength makes its ductile and prevent micro cracks from widening. Usage of polymers and fibres in concrete is found to be very effective and economical in construction of structures. Even though polymer concrete and fibre concrete are initially costlier by 30-50%, in the long run found to be economical and efficient in carrying various types of loads, including dynamic loads. In this paper, an effort has been made to identify the best suited polymer (or) fibre to impart the functional requirements required for concrete for adoption in the specified structures. POLYMERS & FIBRES IN CONCRETE COMPOSITES Polymers are used in the following manner in concrete. a) b) c) d)
Polymer impregnated concrete. Polymer modified concrete. Polymer coating to concrete. Polymer as bonding.
Fibres are used in concrete as: a) Randomly dispersed fibres in concrete. b) As reinforcement in concrete. c) As an ingredient to produce High Performance Concrete. 493
Characteristics of Polymers & Fibres: Polymers • Improve, strength & ductility • Improve impermeability • Modify flow characteristics of concrete • Improve the bonding properties
Fibres • Increase strength, fatigue and fracture toughness. • Improve post cracking performance. • Energy absorption and matrix form • Sustain increased deformation.
Commonly used Polymers and Fibres: Commonly used Polymers a) Urethanes (Obtained by reaction of polyols) b) Acrylics (Ester of Acrylic & methacrylic acids) c) Styrene butadiene (SB resins) (Synthetic rubber in solution) d) Vinyl (CC polymers such as polyethylene) e) Epoxies (Synthetic polymers)
Common Fibres a) Acrylic b) Nylon c) Glass d) Polyester e) Steel
i. POLYMER CONCRETES: a) Polymer Impregnated Concrete (PIC) Polymer such as Ethyl acrulate, MMA (Methyl Methr Acrylate) are introduced into the concrete to improve its compressive and tensile strength and also to obtain very high early age strength by the following sequence. 494
i)
Concrete is thoroughly dried by heating.
ii)
Dry concrete is evacuated.
iii)
Concrete is immersed in the chosen monomer.
iv)
Pressure is applied.
v)
Impregnated concrete is sealed to avoid loss of monomer.
vi)
The monomer is converted into polymer either by gamma radiation (or) by the thermal catalytic process.
While, by careful mix design concrete with 100 Mpa strength can be obtained in 28 days, by polymer impregnated concrete, strength upto 150 Mpa can be obtained even in 7 days of period. Properties & Applications: Properties are similar to high strength plain concrete. Crack if developed propagate very slowly than that of plain concrete. Has high resistance to acid attack and due to reduced porosity, has low creep and shrinkage. PCC can be used to repair cracked concrete and to improve the durability. PCC has good wear resistant properties and are suitable for application in road surface and floor meant for moving machineries. b) Polymer Modified Concrete (PMC) Polymers are added during mixing to modify the properties. They are added either as an aqueous emulsion (or) in a dispersed form. These polymers when mixed with concrete makes it more workable and hence w/c ratio can be reduced. Hence, flexural strength and compress strength gets increased. Poly Vinyl Acetate (PVA) copolymers though costlier are useful in power plants and in pedestals of launch vehicles applications. 495
i)
For improving factory floors.
ii)
In loading / unloading ramps.
iii)
For repairs to spalling concrete.
iv)
In cementing ceramic tiles to RCC.
c) Polymer Concrete (PC) Monomer (or) resin is added to bind reheated aggregates consisting of coarse, fine, ultra fine and other particle substances. Commonly used binders are styrene, polysters, MMA (Methyl Methr Acrylate) etc. applied by adopting one of the following methods: i) Prepack method: Graded during aggregates are packed in moulds and polymer is poured into the voids and if necessary impregnated by vacuum process. ii) Premix method: Polymer and aggregates are mixed in conventional mixers and the mix is transferred to moulds and vibrates. Polymer concrete is highly resistant to chemical attack and can develop compressive strength upto 1200 mg/cm2. Resistant to water absorption and hence suitable for water retaining structures. d) Polymer Composites: (P. Com) They are produced using polymers with sand / aggregate and cement - Fatigue resistance and resistance to wear and tear improves with polymers and hence suitable for: i)
Pre-cast items
ii) Industrial floors. iii) Conduits carrying chemicals. iv) Linings in tunnels and cuttings. 496
ii)
RAIL CORROSION CONTROL MEASURE USING GLASS CLOTH CARRIER (FIBRES)
Corrosion on the foot of the rail inside the track due to toilet discharge from trains is mitigated by the following methods by pasting layers of glass cloth carrier (confirming to IS 11273-1997) using Araldite (resinXY-27 & hardner XY-28 in the ratio 100:40) approved by RDSO for manufacture of Glued Joints. 1.
CORROSION PREVENTION:
By wrapping a single layer of glass cloth carrier (0.3mm thick) on the gauge face side of foot, half web and half bottom width of foot, corrosion is prevented to a large extent and in the process, a) Rail flange gets protected against corrosion. b) Toe load gets increased by 10-15% c) Rail gets partial insulation against variation in rail temperature d) Due to reinforcing action, fracture gets controlled.
2. RETROFITTING THE RAIL AT LOCATIONS OF LINER SEAT CONTACT CORROSION: By pasting 3-4 layers of glass cloth carrier (app 1mm total thick) over short bits of 250 to 300mm length on the surface of inner foot of the rail, at the earlier locations of liner seat contact(Now coming to mid span between sleepers during interchanging of rail), a) Tensile flange of the rail gets strengthened b) Growth of further corrosion at this location is prevented c) Elasticity of the rail track gets increased and hence reduced brittleness. 497
3. COST • App. Cost of preventive single layer for laying inside of 1 track km is Rs.45000. (Against Epoxy painting of Rs.70000 per track km) • App. Cost of retrofitting at 2x1660 sleeper spacings with 4 layers, works out to Rs.78000 per track km.
4. STUDY RESULTS a) Lab. Tests at EWS/AJJ & IIT/Madras
i)
Gluing the glass fibres over rail foot has increased the breaking strength of specimen by app. 20% 60kg 90 UTS corroded rail (5mm only available thickness) has broken at 110t whereas glass cloth carrier reinforced rail of same extent of corrosion has broken at 136t.
ii) Cyclic load test (Fatigue test) carried out at Structural Engineering lab of IIT-Madras indicated that a specimen retrofitted at liner seat corroded locations with 4 layers has not failed even at 5 million cycles of load (Normally for weld test, minimum load prescribed is 2mil cycles) and is not likely to fail in fatigue since ENDURANCE limit has reached. iii) To retrofit, the corroded surface was cleaned by mechanical wire brush, “rust converter” chemical was applied to clear the rust and convert by oxidation into a bonding surface, and thereafter Araldite glue was applied. iv) Length of fibre reinforcement= corroded length + 2x(Develop. length=16xtotal thickness of fibre layers).
498
v) The strength enhancement varies with respect to number of fibre layers glued but there is a limit for strength enhancement, as more number of layers glued will reduce the ductility. vi) To clear the doubt on pattern of signals with and without reinforcement, USFD testing has been done, and it is clarified that glass cloth reinforcement does not affect signal reception in USFD testing. vii) Inelastic behavior is more dominant with corroded rails and ductile behaviour with glass reinforced corroded rail. viii) No direct correlation of breaking load with the extent of corrosion (available thickness of foot) could be established. ix) Hardness in-and-around corroded locations is much higher (286 BHN) than that at non-corroded locations, indicating brittle patches and proneness for sudden failures at corroded locations. The hardness was as high as 286 BHN as against 260 BHN in non-corroded locations. x)
It is recommended that at least 50 cm on either side of weld, glass cloth reinforcement to be removed, before welding.
xi) Based on Load-Deflection curve for various samples retrofitted with 4,6,8,10 layers etc, it is noted that 4 to 6 layers is adequate to attain the strength of original rail. xii) By keeping the retrofitted rail in inverted position, static bending test was carried out (so that the glass cloth carrier will be in compression) and it was noted that no delamination has occurred till fracture. Tests are not conclusive. ….3 499
b) Field study at Km.554, 555 & 556 near TY (Madurai-Tuticorin section) i) At Km.555-556 between TY & SRT, on a sanctioned stretch of TRR, new 10 RP rails have been pasted with one single layer of glass cloth (0.3mm thick and 70 mm wide) on the top of the rail foot in a continuous manner and ERC were driven on the above pasted surface, over 1km length. ii) The released rail having severe corrosion (Left over thickness of rail foot = app 5 to 6mm) has been retrofitted by pasting 4 layers of glass cloth carrier at all the corroded bits in lengths varying from 200 to 250mm over app. 0.8 km at km.557-558.. Out of the 4 layers, 2 alternate layers have been wound and taken to the bottom of the rail foot. This is found to be more effective method than pasting on the top of rail foot alone, due to continuity at the bottom edge of rail. The studies/Field trial reveal that i)
Single layer pasting of glass cloth carrier is able to withstand 3 or 4 repeated driving of metal liners, without exposing the rail surface.
ii)
After retrofitting work completed in Feb 2011 (with 4 layers) at this 1 km stretch (Km.554-555), no fracture has occurred till now. (Earlier on the same 1 km rail in the year 2008 to 2010, 3 fractures have occurred.)
iii)
No corrosion patch was noticed around the liners, on this section having 5 nos. of morning trains.
iv) Temperature variations were noted continuously in the full month of May 2011 and with Δ T=28°, the pasted glass cloth was found intact.
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5.
FUTURE STUDIES PROPOSED
i.
Glass cloth carrier of higher thickness (0.4mm) is also available in the market. Trial is proposed to be taken up with this higher thickness of cloth.
ii.
In glass cloth carrier, in addition to square mesh, diagonal pattern mesh (Inter woven) are also available. This will give more resistance in all directions (Multi directional reinforcement) and this is proposed for trial near CGL (Up line).
iii.
Sprinkling fine sand on application of glue to improve the inter surface bonding (By the protruding sand particles).
iv.
Gluing glass cloth and wrapping around the metal liner (over full area) with single layer of glass cloth carrier and driving on the track, to avoid metal to metal contact corrosion.
iii) FIBRE REINFORCED CONCRETE: (FRC) Brittle materials such as glass and carbon can acquire enormous strength and stiffness when produced in the form of fibre. Addition of these fibres to a weak, compliant matrix results in a material (composite) that has greater mechanical properties than its constituents. The above composites can be customized to dimensions. FRC can be used to carry loads efficiently over a)
Pile caps.
b)
Pavements and machine foundations.
c)
Repair to cracks.
d)
As slurry in asbestos cement.
501
Recent study has revealed that FRC can be made even with 20% fibres by volume along with super plasticizers and microsilicas. Strength of concrete thus can be enhanced to almost double both in compression as well as in tension. Properties of FRC are influenced by the type of fibre volume fraction of fibre, aspect ratio (Length / diameter) and orientation of fibres in matrix. Behaviour in compression: With fibres in the concrete, stress-strain characters change substantially particularly after development of initial crack. Toughness get increased in the ultimate range and hence is suitable for catering to dynamic loads such as earthquake loads. Energy absorption properties increase with increase in quantum of fibres and with confining steel fibres in horizontal direction. In Tension: In tension, fibres in the concrete matrix share the tensile load initially till cracking occurs and thereafter carry the load upto the full carrying capacity of fibres. This is a predominant feature of FRC and this mechanism gives rise to favourable dynamic properties both in energy absorption and fracture toughness. Predominant fibre pull out due to disbanding of fibre results in additional energy dissipation and hence can cater to more dynamic load and fatigue loads. FRC for earthquake zones: Non-linear behaviour and ductility are of great importance in design of FRC for catering to lateral loads. Structure with FRC designed for earthquake though may get minor damage, shall not 502
collapse in the post elastic range and this can be achieved by fibres embedded in the FRC. Maximum deflection fmax fmax ---------------------------------- = -------Elastic deflection fy fy Ductility factor µ
= fmax -------fy Therefore, fy = 1/µ = fmax From the above, with increase in ductility factor, forces on the structural members are reduced. By proper design of fibres, its volume, aspect ratio etc, FRC can be made to acquire large scale ductility and hence carry more dynamic loads. Various types of fibres can also be combined as additives with concrete to attain a high performance fibre reinforced hybrid composite to achieve optimum mechanical behaviour. Tests for FRC i)
Pull off method - Developed by Danish Tech. Lab. as LOK test (Patented).
ii)
Random compressive strength test – CAPO test (Inverted Cap Pull out test) developed in Denmark to indicate the internal state of cracking in FRC.
iii)
Break off test - Flextural strength determined by breeding a slot of concrete - Developed by Norwegian Tech. University.
iv)
Kelly ball test - To decide the workability of FRC using a hemispherical ball developed by Kelly.
v)
Figg’s permeability test - By Building Research Establishment. U.K. 503
IV) a)
COMPOSITE CONCRETES: Smart concrete:
The concrete that has the capability and ability to adapt itself to the environment. Concept of smart concrete is based on the ability of bones to grow and repair by itself, provided adequate nutrients are supplied. Common bacterium “Baccillus Pasteruii” when mixed with concrete produces highly impermeable layer of calcite over the surface and closes minor cracks and thus self repairing the structure itself. Smart concrete / bacterial concrete is preferred since i)
Increased resistance to sulphate and alkali attacks.
ii)
Plastic shrinkage cracks are reduced.
iii)
Due to impervious layer formed, penetration of harmful gases and chemicals into the concrete is prevented and hence corrosion in reinforcement gets reduced.
iv)
Increased compressive strength by 5 -10%.
b)
Nano composite:
Natural bio-nano composite material such as natural bone when made as a composite has revealed improved recovery against cracking with very less plastic strain. HAP (Hydroxypatile) polymer composite can be used to form concrete-composite by soaking it in water and body fluids (Prepared using Nacl, Cacl2, Na2SO4, K2 HPO4,…etc) with strengths upto 80 Mpa. Another nano composite NACRE is used to improve the strength and toughness of concrete. NACRE is a ceramic laminated composite, consisting of organized polygonal shaped aragonotic platelet layers of 0.5 µm thickness and separated by them 10-30nm layers of organic matter. 504
DEEP SCREENING OF YARD MAIN LINES BY BCM’S FOR IMPROVING THE IN-SERVICE RELIABILITY OF RAILS AND WELDS - B. Krishna Reddy, Sr. DEN/S.C.Railway - T. Anil Kumar, A. DEN/S.C.Railway
__________________________________________________ Abstract: At present deep screening of all yard lines are being done by manual means only. Deep screening of points and crossing of late started by BCMs. This has helped in improving the running over points by great extent. The TGI values in yards are particularly very bad when compared to block section. This is mainly because of poor condition of track in yards. The resilience of track mainly depends on the condition of ballast quality and its cushion. The poor cushion in yards is one of the major reasons for rail/weld failures in yards. 1.0 Introduction: The present method of manual deep screening in yards has the following disadvantages: 1. Restrictive caution order of 20Kmph for 1-2 weeks 2. Requirement of Banker if yard has steep approach gradients 3. Slow relaxation of caution order 4. Quality of work has been issue all the time 5. Management of work spot for longer time and the safety issues involved with it. 6. The screening of ballast is mostly done by placing screen on platforms, which causes nuisance to passengers. Deep screening of yards with BCMs has not been attempted so for, mainly because of the problem of muck disposal and S&T involvement to major extent. 505
2.0 Case study The running on Nekkonda yard lines (KZJ-BZA) was not satisfactory and from records it is observed that last deep screening was done more than decade back. The clear cushion was found to be less than 100mm at many locations. The only option to improve track running was to improve track resilience by screening ballast. Instead of going ahead with manual deep screening it was decided to go for mechanical by using BCMs. The main problem in this method is of the muck disposal and availability of longer blocks. It decided to screen the entire yard line of 750m in single block with two BCMs, CSM, DUO, and DGS. As it was decided to screen the entire 750m length in one go and to open the traffic at higher speed, this needed longer block hours. This process of screening involves blocking two lines at the time of work. The yard plan is shown in annexure 1. \ First option was to block one main line for BCMs and the respective loop for placing BOBYN’s. Advantages 1. Traffic on one of the lines (UP/DN) can be normal Disadvantages 1. Getting longer blocks are not easy in highly saturated routes. 2. Discourages operating department to give longer block Second option was to block both main lines, one for BCMs and other for placing BOBYNs. Advantages 1. Blocking of both lines is easy as it can permit traffic on loop lines. 2. Encourages operating department to give longer block 506
Disadvantages 1. All traffic has to go via loop lines only at restricted speed. Both schemes were discussed with operating department. Keeping the importance of the section and non availability of longer blocks it was decided to go with second option 3.0 Advance preparation Sample pits were dug to see the condition ballast, cushion and expected muck. In South Central railways, the normal ballast rake consists of 30BOBYNs. As it was decided to work with two BCMs, this became limiting factor for length of spacing between two cutter bars. The schematic diagram of placement of track machines is shown in annexure 1. Just before the actual work stared, three cutter bars are provided at 0,200,600M length. 4.0 Advance planning 3
1. Dumping about 300M ballast in each line well in advance. This is to avoid ballast shortage immediately after screening which helps in facilitating two rounds of packing and opening the track at higher speed. 2. Joint survey was conducted with S&T with cable locator and identified all possible cable locations. This was verified duly opening ballast at site. 3. Joint survey with TRD supervisors to locate OHE bond wires. 4. Foot survey to identify any physical obstructions like FOB columns etc. 5. Availability of empty BOBYN rake (30 wagons) with power. 6. One tractor compressor and two hand breakers are kept ready to use in case of finding any obstruction like old S&T foundation etc 7. Two sets of gas cutting equipment are kept ready to remove rail pegs etc 507
Before starting the block presence of one signal inspector, TRD supervisor and traffic inspector was ensured to see that normal traffic movement was not affected even in case of some S&T failure. 5.0 Execution It was decided to first to screen the DN main line (750m). Before the commencement of block, empty BOBYN rake is placed on UP mainline. Then brought BCM1-CSM-BCM2 on to DN main line. Cutter bas are provided at 0m, 200m, 600m chainage. The order of machine deployment was BCM1, CSM, BCM2, DUO, DGS with BCM1 leading. Started screening from 0m chainage by BCM2. Same time started BCM1 at 200m ahead. CSM started tamping behind BCM1. After 80m screening done by BCM2, DUOMATIC and DGS were brought to rear of BCM2. This was done to avoid rear end fouling to adjacent loop line by DUOMAT and DGS and it also helps to screen longer length. It avoids occupation beyond starter signal and also helps in signal and traffic interruption to DN loop line. Behind each BCM, sufficient men were deputed to fill up deficient ballast. Screening for 400m is completed in 2hrs by both BCMs. Meantime tamping by CSM, DUOMATIC and vibrating by DGS was in progress. Empty BOBYNs were pulled forward to cater for muck unloading into empty wagons while screening was in progress. BCM1 cutter is left at 400m chainage, this BCM1 was moved to next cutter bar pit at 525m where spare cutter bar is kept ready in pit and started screening. For BCM2 cutter bar is taken out at 200m, machine brought forward to 400m chainage, utilized BCM1 cutter bar and started screening. Behind each BCM, CSM, DUOMATIC gauge level is taken, if any variation observed, immediately informed to operators for adjustment. As starter signal approached, main S&T cables crossings and old foundations encountered, progress became slow and it took 2hrs time for balance 125m. CSM and DUOMAT packing done with double insertion. After completing screening, one 508
extra round DGS was operated. All cutter bars taken out from track and ballast filled. The traffic Opened at 40kmph. The whole process completed in 4.30hrs.
In the following day UP Line deep screening was completed duly placing BOBYN wagons on DN Line.
509
6.0 Muck disposal There are two options for muck disposal. First one was to take the wagons to nearby ballast depot or other unloading platform and unload the muck using mechanical means. Second was to take the wagons to nearby long girder bridge and to unload the muck in to the dry river bed and later it can be removed. As we had a major girder bridge nearby, Wagons were moved to the bridge and unloaded the muck.
The muck also can be used to make good cess also.
510
7.0 Precautions 1. Advance inspection with S&T supervisors is mandatory. Any cable cut may lead to major disruption of traffic 2. Presence of S&T and Traffic inspector is must while the work is in progress 3. This method is suitable to screen non platform lines only 4. Sufficient ballast must be unloaded in advance so that ballast deficiency will not arise immediately after screening. This also helps to open traffic at higher speed. 5. Sufficient care to be taken while dumping muck in to wagons so that muck doesn’t fall on screened track. 8.0 Conclusion So far deep screening in yards is to be a tiresome and prolonged exercise. With this method of screening, if planned properly we can complete both lines screening in just two days. Traffic can be opened at higher speed and the relaxation of speed restriction is very fast. This will greatly help in reduction of rail/weld failures and also best quality of running can be obtained.
511
512
INDIA NEEDS MORE DMRCS OR MORE MRVCS? - K Venkateswara Rao, IRSE, GM/RITES/Secunderabad __________________________________________________________________________
Synopsis: Today, “Metro Rail” has become the buzz word for all urban transport planners of India. It is being perceived as one stop solution for all urban transport problems. Due to huge costs associated, it is not able to cover any given city fully. Also, many cities are not able to go for it. In the light of this scenario, certain urban transport basics which are not getting deserved attention are put in their right perspective in this article. 1. Urban Transport: Basics Redefined • Urban settlements grow by: o Geographical Expansions o Getting dense and over dense • Commuting needs of geographical expansions of habitations are handled by bus up to certain extent and by rail beyond that. • Dense habitations are handled by bus and over dense habitations are handled by Metro Rail.
Geographical Expansion of urbanization needs local trains & Local Trains expands urbanization geographically (eg: CIDCO) • These different modes of commuting also have reverse effect: o As local train network increases, urbanization expands geographically. The classic example is CIDCO model of Mumbai. 513
o As metro rail network increases, urbanization becomes dense and over dense.
Over dense urban areas need Metro Rail & Metro Rail makes the urban areasover dense • Thus options for urban planners are: o Expand geographically the settlements. o Densify and over densify the settlements. Optimal mix of the above two strategies make a good urban planning. 2. Which mode is more suitable for commuters? • Any commuter selects the mode based on the journey time; i.e whichever mode takes least journey time, he selects that mode.
• The journey time is dependent on the trip length (distance from his residence to office) and the level of urbanization. Even if trip length is less, if urbanization is more, journey time becomes more (due to traffic jams etc). • Modes that best suited for a particular trip length and level of urbanization are typically depicted as under: 514
Level of Urbanization
Mrtro Rail Private Transport
Bus
Train
Commuting Trip Length From the above, it can be clearly seen that: • Metros can cater for highly urbanized scenario but can offer only shorter trip lengths. • Theoretically metro can cater to any trip length. But, its prohibitively expensive nature limits its reach and trip lengths. • Trains can cater for semi-urbanized and urbanized areas and can offer more trip lengths of the order of 100 to 150 Kms (Mumbai - Pune is the classic example). 3. Commuting or Nightmare? What is the way out? It is not exaggeration to term the commuting a nightmare. Traffic jams in cities like Bangalore, Kolkotta, Chennai, etc are making the commuting experience a nightmare. Many such cities are contemplating Metro Rail. But, unable to move ahead due to heavy costs involved. All these cities are required to re-work their urban planning strategies duly considering Rail network as an integral part of commuter service.
515
4. Which should come first to any city? Local Trains or Metro Rail? • Given the huge cost implications and cost difference between metro rail and local trains, trains should be the first option naturally. • Metros can be constructed on limited scale. But expanding them to throughout the city may not be possible due to heavy costs. A city or two (like Delhi) can have. But tens and hundreds of Indian cities where commuting is gradually becoming a nightmare cannot afford metro rail. • Therefore, experiments like MRVC and CIDCO need to be undertaken by many cities rather than jumping directly like DMRC. 5. Metro Rail: Need for judicious alignment • As could be seen in the depiction above, metro is expected to ease out the traffic jams caused by busses. • Therefore, prima-facie, it should follow the alignment of heaviest congested road alignment of the city. • While doing so, care should be taken that the alignment is not very close to the railway line. If this care is taken, the heavy investment made on Metro rail ends up duplicating the service that can be conveniently offered by rail net work at much lesser costs. • While Delhi metro appears to have been judicious in this aspect, Bangalore metro does not appear so. Substantial portion of Bangalore metro phase-I (20 to 25 Km out of 42 Km) is very close to rail network. • Due to this close proximity of the alignment, some public forums are even commenting that Bangalore Metro fears a threat from local trains and therefore is opposing development 516
of commuter rail system in Bangalore 1. If this is true, investment of billions and billions borrowed money may not be worth.
Metro Rail and Sub-urban trains should supplement each other Then should not be competitors as being perceived in Bangalore 6. Difficulty to deal with Railways – A major hurdle to urban transport planners • Urban transport planners in India may prefer to go for Metro Rail rather than local trains. • Main reason for such a tendency is the difficulty to deal with Railways. The proposal needs to be examined by 3 tier set up (Division, Zonal Head Quarters and Board) and by all departments (Civil, Electrical, Mechanical, S&T and Traffic) at all three levels. All these hierarchical set up may not maintain consistency in their approach may not show any commitment for the issue. To this extent, IR needs to change its model of thinking and working.
7. Conclusions: India needs more MRVCs than DMRCs a) Due to heavy costs involved, before going for Metro Rail, urban transport basics need redefinition as discussed in paragraph 1. b) Facilities to commute about 100 to 150 Km in reasonable time should be the primary parameter in any urban planning.
1
http://praja.in/en/projects/3110/announcement/controversy-brewing-commuterrail-metro-blame#comment-32576 517
c) For such a requirement, MRVC like organizations should come up in all major cities before DMRC like organizations come. d) Option of Metro rail should be explored only after potential of sub-urban train system is exploited fully i.e as in case of Mumbai. e) In this context, Mumbai model [i.e developing local train system first (like MRVC and CIDCO model), and going for metro rail next] should be taken as role model for all cities instead of directly jumping for metro rail. f) Indian Railways should redefine its commitment to commuter service and strive to bring more MRVCs (for Hyderabad, Bangalore, Chennai etc) than DMRCs. g) If this strategy is not followed: • India will end up with Metro Rail for a few cities that too for a few Kms leaving rest of the public and rest of the cities in their nightmarish commuting. • India may get into an irreversible debt trap (due to huge debt financing of metro projects).
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IMPROVING THE IN-SERVICE RELIABILITY OF RAILS AND RAIL WELD PROBLEM OF CORROSION & BREAKING OF PLATE SCREW AND ITS REMEDY - A. A. Pathan, SSE(P.Way) /JAO __________________________________________________________________________
Screws spikes of 20 mm dia. called plate screws are used to fasten anti creep bearing plats/ slide chairs with wooden Sleepers ,screws spikes of 22 mm/ 24 mm dia. called rail screws are used with wooden sleepers with or without bearing Plates and also used with PRC sleepers. Corrosion of rail screws: The acid gases (in the form toilet water / night soil) dissolve in the film of moisture coating the Screws are more harmful to cause of corrosion than dampness. Prevention: 1. Always use correct size screws as per requirement. Drawing No. T 3911 T3912 T3913 T3915 T4153 T1035 T10674 T10675 T10676
Length 140 150 160 180 151 135 110 132 120
Dia. 24 MM 24 MM 24 MM 24 MM 24 MM 22 MM 22 MM 22 MM 22 MM 519
Use. PRC PRC PRC SEJ BR. Approach for wooden sleepers for wooden sleepers for wooden sleepers for wooden sleepers
2. Always used galvanized /metalized /painted screws and when traces of corrosion appear on the galvanized /metalized surface of screws, than these should be taken up for painting or replacing. 3. Do not use the hammer for tightening of screw. 4. Proper combination of fitting /rubber pad should be used between the rail foot and sleepers, because the friction offered by rubber pad also helps in arresting the lateral deformation / movement of the rail. 5. Before tightening the screws in the sleeper, anticorrosive treatment should be given after cleaning dust & rust from the screws & inside hole of dowel, than immersion of screws in bituminous emulsion paint 6. Apply grease on screws surface & inside of dowel. A sound track is an important prerequisite for the economic growth of railway. To meet the challenge of higher speed, higher density of traffic and capable of offering adequate lateral resistance to the track. A screws plays a very important part of track because it holds all lateral forces & and thrust of shear forces act on the point & crossing, curve & SEJ. This will help in streamlining the periodicity of overhauling of screws .The screws should be driven properly to ensure that the screws head is flush with the plats and on rail flange .The square ness of sleepers should be ensured during laying & maintenance to avoid twisting torque between screws & sleepers.
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Guide line for repairing of concrete sleepers after braking plate’s screws inside nylon dowel. I, started repair of broken plate screws sleepers in the track since 2006 & hundreds of sleepers repaired successfully. Procedure of repairing is given below: 1. The fastenings screws etc are removed, sleepers shall be cleaned of all dust. 2. Gas cutting equipment flame for heating the broken screw in side the dowel. 3. A 20 mm size MS pipe shall be pushed in side the dowel with the help of hammer & twist anti clock wise with the help of cross bar, then the broken screw piece will come out. 4. Clean the inside surface of sleeper hole, where the new dowel is to be placed by using special made cutter tool of M steel ,which have same size & shape of outer shape dowel, by re- boaring to scrap off loose nylon fibers from the hole . 5 Get tight one new screw in side the dowel. 6. Apply epoxy over outer surface of nylon dowels and also in side the sleeper hole. 7 Tight the dowel inside the sleepers hole with the help of spanner. 8. Filling some epoxy around the top face of dowel and sleeper gap. 9. Remove the screw from dowel. Now the sleeper is ready for use
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Benefits: 1. Operation not req. any traffic block. 2. All operation are carried out without disturbing the sleepers. 3. Minimum tools requires 4. App. 30 minutes time taken for repair of one broken screw. 5. No changes appear in strength after repair of sleeper. 6. One technician and one khallasi can do this work. COST ANALYSIS – Cost wise it is very cheap and economic. Repair cost of one broken screw: 1. Gas cutting equipment (in Rs.) -- 20.00 2. Epoxy (in Rs.) -- 30.00 3. Nylon dowel (in Rs.) -- 27.00 4. Labour -- 25.00 TOTAL = 102.00 Suggestion for minimize the breaking of plate screw in T/Out sleeper. 1 Do periodical greasing of plate screws and always keep plate screws in tight position. 2. Keep proper alignment of T/Out. 3. A modification is required in PSC Sleepers of T/Out. On sleeper no 5 to 27 of 1: 12 T/Out, sleeper no 5 to 16 in 1:8.5 T/Out and diamond crossing switch portion, there should be provision of extra ERC insert at the end of S/chairs and special Bearing plates to resist extra thrust in switch portion due to sudden change in curvature on curved T/Rail side. 522
Heat the dowel using Oxy acetylene flame and insert a 20 mm MS pipe with the help of hammer. Twist the pipe anti clock wise with the help of cross bar. The broken screw piece will come out.
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INSTALLATION OF BALLASTLESS TRACK TURN OUT IN BANGALORE METRO RAIL PROJECT - A.S. RAJAGOPAL, Rtd, Dy CE/SWRLY - V.N. SEETHARAMAN, Ex JE/ PWAY/SWRLY
________________________________________________________ Synopsis: Bangalore Metro has adopted ‘Ballastless Track’ as the standard track for the elevated and underground sections and such as At Grade. The Turnout assembly in these sections is also with ballastless track. “Top down construction” method is followed in construction of ballastless track and turnout. The mode of traction is 750v DC, third rail system. In Depot the track & turnouts are generally laid with PSC sleepers. (Ballasted Track), The method of construction of Ballastless Track in Turn outs is presented in this paper. 1. Stages Involved in Installation Ballastless Track Turnout 2.1. General. The turnouts used in this project are 1 in 9,300m radius and 1 in 7, 140m radius. The entire turnout installation is divided into slab generally saying from 3m-5m in length with gaps of 200mm between the plinths to facilitate easy construction and drainage. This gap is helpful for drainage purpose to lead off the surface water in to the drainage spouts provided in the Viaduct segments. The plinth lengths are so adjusted that they do not fall in the segment joints. This is necessary to ensure continuity of earthing bars placed for stray current collection and leading to pier foundations for earthing. 1 in9 turn out is normally constructed with 9 slabs and 1 in 7 turnout with 6 slabs. 525
2.2. Stages involved in installation I.
Survey work
II.
Assembly of Turnout
III.
Adjustment of position of turn out
IV.
Preliminary works.
V.
Final Adjustment & Concreting
VI.
Finishing work & Cleaning
VII.
Curing
VIII.
Removal of formwork & Jigs
IX.
Cleaning / Miscellaneous
X.
Thermit welding of Rail joints.
XI.
Checking turn out for laid down Tolerances
2.2.1 Survey work. The survey work is carried out using modern survey instruments such as Auto levels & Total stations. The chainages of all characteristic points of the turnout for straight track, and turnout, such as SRJ, Heel of Crossing etc are marked by paint on the side wall of viaduct parapet and on the viaduct surface. The survey team will install the reference marks giving the "Top of Rail" (T.O.R.), at various points. ●
Center line of main line & turnout on viaduct will be set out using of total station instrument.
●
Components of turnout i.e. switches and crossings are lifted with a gantry crane of 1-2 tons capacity hoist or by hydraulic jacks 15 tons capacity and placed on temporary wooden supports in final position . Rail joints are held in position using fishplates & ‘C’ clamps. 526
Turnout lifting
Gauge Adjusting Bar
C clamp
• •
•
•
Turnout components are lifted by 12 special gauge lifting bars (location shown in the figure) which can adjust line and level. Gauge / alignment of switch and crossing are checked to ensure these are as per drawing and are within tolerances and all temporary supports removed. After confirming that the switch assembly and crossing are in the correct line / level, rails for lead portion of straight track and turnout are placed in correct position to proper gauge / line and these are to be within the tolerances. Fastening system at location specified by manufacturers’ turn outs drawings are then installed. 527
Gantry Crane
Gauge Lifting Bar Photo Showing Gauge Lifting Bar and Gantry Crane
2.2.2
DETAILED ASSEMBLY OF TURNOUT
2.2.2.1 Laying of the half switch, rail and crossing a) Lay the half-switch for straight track first. Check the position of the plates according to the marks on the foot of the stock-rails b) Ensure the straightness of straight stock rail to conform with track alignment (visual check)
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c) Lay the half-switch for diverted alignment, and ensure the squaring of the half-switches at the end of stock rails. If required, move the curved half switch forward and backward. d) Lay the crossing, and ensure the correct distance ‘x’ between toe of switch and actual nose of the crossing in accordance with the layout drawing. If required, move the crossing forward or backward.
Laying half-switches and crossing
e) Lay the two external rails of the lead portion (R1and R4) as well as the 2 closure rails of the crossing (R2 and R3), duly checking the correct orientation.
Laying intermediate part and closure rails of crossing
f) Ensure visually the straightness and alignment of straight external rail. 529
g) Check & ensure straightness & alignment of straight external Rail. h)
Rail R2 & R4 in turnout area is to be provided with pre curved insulated rail joint to the required curvature.
2.2.3. Adjustment of position turnout (a)
Adjustment of the switches 1. Adjust straightness and alignment of the overall turnout with a string. 2. Check the track gauge in main track (with gauge) at each base plate location. If the track gauge is out of tolerance, move the curved half switch (not the straight which is the reference switch) 3. Check the track gauge in diverging track (with gauge) at each base plate. If the track gauge is out of tolerance, move the curved half switch, and check again the track gauge in main track. 4. When completed, put clamps to fix the stock rail and switch rail together and ensure there is 1 mm maximum gap on the contact between switch and stock rail (with filler gauge) and 2mm maximum between switch rail and stop.
(b)
Adjustment of the intermediate part and crossing 1. Check the track gauge in main track (with gauge) at each base plate. If the track gauge is out of tolerance, move the crossings (not the external straight rails which are the reference of turnout). 2. Put in place the straight lead rail (R3). Check gap at each side. Check the track gauge at each base plate location. 530
3. Put in place the turnout lead rail (R2). Check the versine of curved rail. Ensure 5 mm gap at each end. Check the track gauge at each base plate location. 4. When completed, check the track gauge in the turnout track. If the track gauge is out of tolerance, move the external curved rails for adjusting track gauge. 5. Check and ensure correct clearances in check rails opposite to nose of crossing. If these need adjustments, provide shims / liners behind check rails. 2.2.4. PRELIMINARY WORKS 2.2.4.1 Leveling and Lining jigs Special leveling and lining jigs are installed. These jigs will allow the turnout to be lifted to its final level. As soon as the jigs are installed, the wooden supports are removed and pre adjustment of level and line are performed. The pre-adjustment is done according to the data marked on the parapet wall or on the top surface the viaduct. 2.2.4.2 Rebar fixing /Formwork / Miscellaneous After preliminary adjustment of switch assembly, crossing etc, rebar placing and formwork can be installed as follows: • Turnout slab will be segmented and gapped as per detailed approved shop drawings • Place reinforcement bar in position, tie up longitudinal and transverse rebar by wire/ plastic clip. • All sleeves for signaling or power cables are to be laid in correct position. • Dummy rail (in lieu of curved glued joints of turn out) will be fixed with the clamps with the adjacent rails the rail level will be the reference to the construction and all the levels should be checked accordingly. • Anchor bolts of fasteners are fixed vertically. 531
2.2.4.3 Stray Current connection: • The path of the return current is through the running rail. In case this return current gets leaked to the structure there will be corrosion of the reinforcement bar due to electrolytic effect. It is estimated that if this leakage is not properly detected and controlled the entire structure will fail. To avoid this stray current corrosion, proper stray current collection mesh is provided and connected to earth terminal points at nominated pier locations. • Plastic dowel for third rail bracket shall be installed at designed locations to facilitate casting of third rail pedestal requested for fixing third rail. • Formwork should be placed and adjusted. The shuttering arrangement fixed should be rigid. All the gaps on the sides should be properly plugged so that no concrete/mortar escapes out. • Proper gaps in shuttering should be provided to ensure drainage in track plinth and also necessary openings required for providing signaling rods and other fixtures of signaling equipments.
Shuttering after Fixing Rebar Cage of Turnouts Slab 532
2.2.5FINAL ADJUSTMENT & CONCRETING 2.2.5.1 Final Adjustment of turnout • Before concreting, the survey team shall check the control alignment, level and gauge of the turnout and proceed with the necessary corrections to obtain the final adjustment. • Gauge, alignment & level will be checked as per Inspection Test Plan(ITP) 2.2.5.2 Track bed Preparation • Prior to concreting, track bed will be kept humid for at least 12 hours. This enables the track bed to be saturated with water and therefore avoid cast concrete to dry at the interface of 2nd layer concrete and 1st layer concrete.
2.2.5.3 Concreting • Preparation of the area: the area to be concreted is cleaned by compressed air (blowing), and reinforcement bars and first stage concrete humidified. • "Protection" (plastic covers) is installed on equipment and fastenings, rails, stock rails, tongues, closure rails to prevent concrete/ mortar comes in contact with these. • As per the quality procedure, all required checks will be made and the details recorded in the checklist formats before approval for the casting. • Ready mix concrete will be transported by road through transit mixers from the batching plant to the concrete pump located at work spot.
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• After the approval by engineer in charge concreting can be started. Concreting should not be done during rains. Protective plastic sheets should be kept ready for use in case of unexpected rains. • Turnout slab are cast into 6 slabs in case of 1 in 7 turn out and 9 slabs in case of 1 in 9 turn out and these are cast as per following sequence: o Concrete the base concrete slab on the first day. Needle vibrator is used for proper compaction of concrete to avoid any voids. At the end of concreting, when the concrete is still fresh, laitance at top of concrete where second pour concrete is to be laid should be removed and concrete surface made rough for bondage with the second concrete. o Second, concrete the upstand wall (anti derailment wall). Before concreting the surface, of previous laid concrete, is roughened, and a layer of cement grout applied for proper bonding. o Grout the underneath gaps of all base plates with nonshrink grout. The dimensions of this layer are 25-40 mm beyond the edge of base plate.
Figure: Showing Segments for concreting Cross over Slab 534
2.2.6 FINISHING WORK AND CLEANING 2.2.6.1 Finishing The surface of concrete is finished using trowels and the components (rails, stock rails, tongue rail, closure rail, check rail, crossing, fastening systems) are cleaned properly.
Figure Showing Non-Shrink Grout and 2nd Concrete Layer under Baseplate (Details of A) 535
2.2.6.2 Protection of concreted surface against rain/wind After finishing the concreting operations, the finished surface should be protected against rain or heavy wind by covering it with a protective layer of plastic sheet 2.2.7. Curing The evaporation retardant and finishing product used for the cleaning of the components of the special track work and for facilitating the finishing of concrete which will remain on the surface of the freshly poured concrete and will combat the effects of drying caused by temperature and wind. The evaporation retardant has a limited time- effect. Therefore, on the consequently following day, water shall be sprayed on the concrete. This operation of water curing by spraying water must be performed for the full curing period, of 14 days taking care to see that moist curing is done continuously. 2.2.7.1 Curing with Water and Hessian Sacks Few hours after the application of the retardant (when the concrete has set), i.e.: 4 to 6 hours, the plastic sheet is removed. Hessian sacks are installed uniformly on the track bed. Water will be distributed uniformly to keep Hessian sacks and the track plinth humid. The track form will be kept humid with Hessian Sacks for 14 days. 2.2.8. Removal of formwork and jigs When the concrete has attained required strength, demoulding of shutters are taken up manually duly ensuring proper care of drainage locations, signaling installations and third rail bracket locations. The shutters are cleaned and moved to stocking area.
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2.2.9 Cleaning / Miscellaneous The turnout is fully cleaned. All rubbish is removed manually by brushing. Then, the surface is blown by compressed air. Before use of the turnout, one temporary connecting rod linking the two tongues is installed and provisional lock device (Point Clamp) is fixed to maintain proper housing of the tongue against the stock rail when trains are running over the turnout. 2.2.10 Thermit welding of Rail Joints All Rail Joints from SRJ to Heel of crossing including the IRJ will be welded with 60 Kg HH Thermit portions adopting SKV process of welding and the weld joints are finished to the tolerances fixed by RDSO. 2.2.11. Tolerances & Finishes. The following are the track tolerances & other parameters to be ensured during installation of ballastless track turnout.
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11.0. General: The concrete up stands (serving as guard rail) are provided on outside where as these are provided inside in case of ordinary track. Labour requirement/ Progress: To complete one turn out installation a batch of about 35 labours will be required for 20 days for 1 in 9 turn out including grouting. Similarly for 1 in 7 turn out a batch of 35 men for 15 days is required. This includes all stages of concreting including grouting, upstand, and third rail pedestal Table: Track Tolerances and Other Parameters for Turnouts S. Description of No. Item 1 Track gauge 2 3 4 5 6
Tolerance Nominal value and tolerances +2/-1mm
Rail inclination Relative displacement b t levelt k Cross
1:20 ± 10% ± 2mm ± 2mm 41-44mm 60mm
Check rail gap Flange way
7
Gap between switch rail and 8 Gap between switch rail and 9 Total Deviation From horizontal li t 10 Total Deviation from vertical li t
± 2mm ± 2mm ± 5mm ± 5mm
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S. Description of No. Item 11 Welding tolerances 12 Ultrasonic inspection
As per Indian Railway Manuals (with latest amendments) for FBW and AT Welds As per Indian Railway Manual for USFD testing with latest correction slips
13 Twist
1:1500
14 Tightening of fastening components
Tightened with Torque of 180-200 Nm bolted fastening system ± 5%. Designed distance between spring clip and rail foot ± 0.2mm
15
Tolerance
Track insulation Track to earth resistance to be measured over discrete sections of track before welding sections to adjacent sections using low voltage earth measuring bridge.(Maximum 1 km sections). Criteria- 100 Ohm- Km or better.
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