Engineering Standard - Track Slab -NSW

Engineerin Engineerin g Standard Civil

ESC 362 TRACK SLABS Vers Versio ion n 1.3 Issu ed Febr February uary 2011

Owner:

Chief Engineer Civil

Approved by:

John Stapleton Principal Engineer Technology & Standards

Authorised by:

Richard Hitch Chief Engineer Civil

Disclaimer This document was prepared for use on the RailCorp Network only. RailCorp makes no warranties, express or implied, that c ompliance with the contents of this document shall be sufficient to ensure safe systems or work or operation. It is the document user’s sole responsibility to ensure that the copy of the document it is viewing is the current version of the document as in use by RailCorp. RailCorp accepts no liability whatsoever in relation to the use of this document by any party, and RailCorp excludes any liability which arises in any manner by the use of this document. Copyright The information in this document is protected by Copyright and no part of this document may be reproduced, altered, stored or transmitted by any person without the prior consent of RailCorp.

UNCONTROLL UNCONTRO LL ED WHEN PRINTED

Page 1 of 14

d r a d n a t S g n i r e e n i g n E

RailCorp Engineering Standard — Civil Track Slabs

ESC 362

Document control Version

Date

1.3

February, 2011

Section 5.7.1 - specify minimum thickness of rail pad when using epoxy grouts

1.2

July, 2010

Correct internal section references throughout; Section 4.12 - change reference to TMC 304 to SPC 301; Section 5.7.4.2 - add guard rail insulation requirements from CTN 08/06

1.1

November, 2009

Change of format for front page, change history and table of contents; minor editing and formatting throughout

1.0

October, 2007

© RailCorp Issued February 2011

Summary of change

First issue of this standard.

UNCONTROLLED WHEN PRINTED

Page 2 of 14 Version 1.3


ESC 362

Contents 1

Purpose, Scope and Appli cati on ...........................................................................................4

2

References ...............................................................................................................................4

2.1

Australian and International Standards .....................................................................................4

2.2

RailCorp Documents .................................................................................................................4

2.3

Other References......................................................................................................................5

3

Definition s and Abbrevi atio ns ...............................................................................................5

4

General Requirements............................................................................................................5

4.1

Use of Track Slabs....................................................................................................................5

4.2

Design Standards......................................................................................................................5

4.3

Integrated Designs ....................................................................................................................6

4.4

Approved Materials ...................................................................................................................6

4.5

Clearances ................................................................................................................................6

4.6

Safety ........................................................................................................................................6

4.7

Protection of the Environment...................................................................................................6

4.8

Heritage.....................................................................................................................................6

4.9

Services.....................................................................................................................................6

4.10

Design Procedure – New or Infrequently Used Products .........................................................7

4.11

Drawing Standards....................................................................................................................7

4.12

Construction ..............................................................................................................................7

4.13

Maintenance..............................................................................................................................7

5

Desi gn Requi rements .............................................................................................................8

5.1

General......................................................................................................................................8

5.2

Design Loads ............................................................................................................................9

5.3

Infill Slabs ................................................................................................................................10

5.4

Width of Track Slab.................................................................................................................10

5.5

Allowable Movements .............................................................................................................10

5.6

Drainage..................................................................................................................................10

5.7

Track Interface ........................................................................................................................10 5.7.1

General ....................................................................................................................10

5.7.2

Slab Construction ....................................................................................................11

5.7.3

Turnouts...................................................................................................................11

5.7.4

Guard Rails..............................................................................................................11 5.7.4.1

General.....................................................................................................11

5.7.4.2

Signalling Interface...................................................................................12

5.8

Noise and Vibration.................................................................................................................13

5.9

Transition Section Trackforms ................................................................................................14

6

Prohibi ted Conf igu rations ....................................................................................................14





1

ESC 362

Purpos e, Scope and Appl ication This Standard details design and performance requirements for track slabs on the RailCorp network. It includes requirements for both rigid and floating slabs, the interface with track, the transition between rigid and floating slabs, and the transition to other forms of track support. It covers track slabs where the track is fixed directly to a concrete slab. This Standard does not address the design requirements for floating slabs supporting ballasted track.

2

References

2.1

Aust ralian and Internation al Standards AS 1170 - 2002 - Structural design actions AS 1726 - 1993 - Geotechnical site investigations AS 2159 - 1995 - Piling – Design and installation AS 3600 - 2001 - Concrete structures AS 5100 - 2004 - Bridge design BS 6177:1982 - Guide to selection and use of elastomeric bearings for vibration isolation of buildings ISO 14837-1:2005 - Mechanical vibration – Ground-borne noise and vibration arising from rail systems – Part 1: General guidance

2.2

RailCorp Docum ents ESC 100 - Civil Technical Maintenance Plan ESC 200 - Track System ESC 210 - Track Geometry and Stability ESC 215 - Transit Space ESC 302 - Defect Limits ESC 310 - Underbridges ESC 340 - Tunnels ESC 420 - Track Drainage SPC 234 - Resilient Fastenings SPC 235 - Resilient Baseplates SPC 301 - Structures Construction





ESC 362

ESG 100.17 - Signal Design Principles Track Circuits SMS-12-PR-0371 - Managing Engineering Design Control

2.3

Other References Workcover Code of Practice - Tunnels under Construction Environment Protection Authority NSW - Interim Guideline for the Assessment of Noise from Rail Infrastructure Projects

3

Definition s and Abbreviations The following defined terms are used in this document: Trackform:

The type of track structure. May be ballasted or non-ballasted. Ballasted trackform consists of ballast, ties, rail fastening assemblies and rails. Non-ballasted trackform consists of concrete slab(s), rail fastening assemblies and rails.

Track Slab:

Concrete slab or slabs with directly fixed track

Rigid Track Slab:

Track slab which is directly fixed to the ground or supporting structure.

Floating Track Slab:

Track slab which is isolated from the ground or supporting structure using resilient bearings.

4

General Requirements

4.1

Use of Track Slabs The use of track slabs may be necessary in the following situations: • •

•

4.2

locations with limited vertical clearance existing tunnels where clearances to the track need to be increased to allow the use of larger rolling stock or to increase the clearance to the overhead wiring new tunnels where the use of non-ballasted track may enable a smaller tunnel profile to be used, ongoing maintenance requirements to be minimised or where the attenuation of noise and vibration is critical.

Desig n Standards Designs are to comply with the requirements of the relevant Australian Standards, specific site geotechnical parameters and the requirements of this Document. Relevant standards and documents include: • • • • • •

AS 1170 - Structural design actions AS 2159 - Piling – Design and installation AS 3600 - Concrete structures AS 5100 - Bridge design AS 1726 - Geotechnical site investigations Workcover Code of Practice - Tunnels under Construction

The design life of track slabs shall be 100 years.





4.3

ESC 362

Integrated Desig ns The design of each track slab is to be integrated taking into account all associated requirements such as drainage, track, overhead wiring, signalling infrastructure, communications services, fire safety equipment and platforms.

4.4

App rov ed Materials Approved construction material for main structural elements is concrete. The use of polymer concrete sleepers embedded into track slabs is approved. Fibre reinforced concrete is not to be used without the approval of the Chief Engineer Civil. Timber and masonry materials shall not be used. Materials in tunnels shall generally be non-flammable and shall comply with specific requirements for fire safety detailed in RailCorp Engineering Standard ESC 340 Tunnels.

4.5

Clearances Horizontal and vertical clearances from slabs to structures adjacent to and over the track are to comply with RailCorp Engineering Standard ESC 215 - Transit Space .

4.6

Safety The design of track slabs is to take into account safety considerations for construction and maintenance personnel, and any other parties including operations personnel who may be required to use the structure. Designs are to incorporate the requirements of the RailCorp Safety Management System, particularly SMS-12-PR-0371 Managing Engineering Design Control. Designs of track slabs in tunnels are also to comply with the requirements of Workcover NSW Code of Practice - Tunnels under Construction.

4.7

Protection of the Environment The design of track slabs is to take into account environmental impacts during construction and maintenance activities, with a view to minimising any impacts.

4.8

Heritage Heritage considerations and classifications must be observed in track slab designs. This may have particular application in circumstances where an existing structure is being refurbished or modified, or where a new structure is being proposed in the vicinity of existing heritage items.

4.9

Services Provision must be made in the design and installation of track slabs for services as required, e.g. signalling, electrical, communications. Services are to be positioned in accordance with the following requirements: •


Transit space standard ESC 215;




• • • • •

ESC 362

Clear of any walking areas where they might present a trip hazard; Not to interfere with or obstruct emergency walkways; Not to obstruct access to or reduce the capacity of refuge areas: Not to obstruct drainage Not to obstruct Track Control Marks.

The location of any services is also to be selected so that future access for maintenance of the services is facilitated.

4.10

Desig n Procedur e – New or Infrequently Used Products If any products specified in the design documentation can reasonably be deemed to be new or infrequently used, these must be identified by the designer and referred to the Chief Engineer, Civil for approval. The designer must be satisfied that the manufacturer/constructor/maintainer understands any special requirements/practices relating to the product prior to release of the design documentation.

4.11

Drawing Standards Construction drawings are to comply with RailCorp’s standard procedures and formats, and are to detail the design loadings, horizontal and vertical clearances, and any other information that is relevant to ensuring that the new structure is constructed and maintained in accordance with the design.

4.12

Construction The design of track slabs is to take into account construction constraints, particularly live road and rail operating conditions and track possession constraints. RailCorp has a suite of technical specifications covering various aspects of civil construction. The specifications are detailed in RailCorp Engineering Specification SPC 301 - Structures Construction and are to be incorporated in design and construction documentation. Construction methods include top down, bottom up or a combination of both. Top down construction involves setting the rails in place with temporary supports and casting the concrete slab in situ. Bottom up involves installing a slab(s) and attaching the rails. Track slab configurations include: • • • • •

4.13

monolithic slab base slab and top slab sleepers embedded in a slab base slab with kerb walls and an infill slab concrete monoblocks embedded in concrete.

Maintenance The design of track slabs is to take into account the ability to access key components for inspection and maintenance purposes. The design shall also consider provision for safe egress from maintenance plant and vehicles onto the track slab. Components, materials and finishes should be chosen to minimise future maintenance.





ESC 362

Maintenance requirements are to be specified in all design documentation for track slabs. Requirements are to include examination tasks and frequencies, damage limits, and repair standards, and be supported by documentation showing the basis for these requirements.

5

Design Requir ements

5.1

General Track slab design is a system design taking into account the stiffness of the: sub-base slab(s) rail fastening assemblies rail.

• • • •

The sub-base is to be designed based on the results of a geotechnical investigation to ensure it provides a continuous uniform support of the track structure. The sub-base shall be designed to prevent the infiltration of water under the track slab and to mitigate against the adverse effects of high water tables. Track slab designs shall: •

•

• • • • • •

Include materials, components and design with proven service history. However, this does not preclude the use of improved track technology that may become available over time (refer to Clause 4.10 above); Be capable of adoption throughout varying configurations of the structure, e.g. in tunnels where configurations may vary between the running tunnel, crossover caverns and underground stations; Minimise the risk of derailment owing to track irregularities; Provide uniform transmission of all rail borne forces to the trackform; Incorporate continuous rail with no mechanical joints; Provide appropriate electrical insulation and electrolysis mitigation measures; Incorporate rail lubrication systems where maintenance requirements dictate; Provide for future track maintenance, including rail replacement, in-situ rail welding and emergency rail clamping.

In addition to the above, the design and installation of floating slabs shall ensure the following: • •

•

•

• •

The dynamic deflections must not cause the transit space to be compromised; The dynamic behaviour of the floating slab must not act adversely with the vehicle suspension modes, resulting in increased wear of any component or a reduction in ride quality; Bearing materials must minimise the increase in dynamic stiffness as the frequency rises. Bearings must be designed and tested in accordance with the requirements of AS5100.4-2004 - Bridge design – Bearings and deck joints and BS 6177:1982 - Guide to selection and use of elastomeric bearings for vibration isolation of buildings; An adequate airgap is provided beneath the floating slab to avoid acoustic coupling effects; Resilient direct fixation of the rails is provided on top of the floating slabs; The maintainability of the trackform is not compromised.

The trackbed vibration isolation systems must be optimised for operation with the rolling stock that is to operate on the track. Where the proposed rolling stock is passenger only, the systems must also be capable of withstanding occasional heavier loads, to account for maintenance trains and other events that differ from normal operations.





ESC 362

The maximum height of grout bed under the rail fixings shall be 60 mm. Packers are not to be used. High impact epoxy grouts/mortars or specially developed grouts are to be used under the rails to accommodate the high dynamic effects and movement of the slab. There shall be no metallic elements in the epoxy. Standard cementitious grouts shall not be used. The grout bed shall provide sufficient edge distance to the bolt to avoid cracking of the grout. Where different trackforms are used on a particular project, the geometric tolerances specified at the wheel/ rail interface should be the same. Different slab trackforms are to be effectively bonded at the interface. The design of track slabs shall provide for easy access to bearings for inspection, maintenance and replacement. Procedures shall be specified in Technical Maintenance Plans. The design shall mitigate against debris getting into gaps around floating slabs. All gaps shall be effectively sealed to prevent debris from entering gaps between structural elements. Non-resilient fastening assemblies are not to be used on track slabs. Where the track slab consists of a base slab and a top slab, the top slab shall be tied to the base slab with anchors.

5.2

Desig n Loads Track slabs shall be designed to accommodate the train loadings as specified below: Operating Class Passenger Main Line / Light Line

200LA plus Impact

Mixed Passenger Freight Main Line

300LA plus Impact

Heavy Freight Option

350LA plus Impact

The loading is based on the railway traffic load in AS 5100 - Bridge design. The ‘Reference Load’ is 300LA. For the other loadings, all axles are to be proportioned by the ratio of the nominated LA load divided by 300. Operating Classes are defined in RailCorp Engineering Standard ESC 200 - Track System. For loadings less than 300LA, future loading requirements need to be considered. Final approval of the design loads shall be obtained from the Chief Engineer, Civil. The impact factor shall be in accordance with the dynamic load allowance in AS 5100 with the characteristic length based on either deck slabs or direct rail fixation. Track slabs shall also be designed for the derailment load requirements of AS 5100. Track slabs shall be designed for earthquake forces in accordance with AS 5100. The earthquake design category shall be Type III i.e. essential to post-earthquake recovery.





5.3

ESC 362

Infil l Slabs Where track slabs are constructed using ‘top down’ methods in which a concrete infill section is provided to connect the track fixings to the base slab, the concrete infill shall be designed and detailed to ensure structural adequacy and durability to give a 100 year design life to AS 5100. In particular the construction joint between the infill concrete and track slab shall be prepared by removing laitance to expose the aggregate using appropriate mechanical equipment. The reinforcement provided in the infill shall be designed to limit cracking due to early thermal and shrinkage effects. Cracks shall not exceed 0.2 mm in width. The infill slab shall be adequately tied down to the main track slab to ensure that debonding does not occur due to dynamic effects or thermal/shrinkage effects. The maximum spacing of the bars shall be 500 mm in any direction. The minimum thickness of the concrete infill shall be 250 mm.

5.4

Width of Track Slab The track slab shall extend a minimum width of 500 mm beyond the fasteners on each side of the running rails at the level of the slab under the rails. The maximum vertical drop at the edges of the track slab shall be 150 mm, unless guard rails are provided.

5.5

All owable Movements The design of the track slab shall provide for allowable movements of the slab that do not adversely affect the integrity of other infrastructure such as track and signalling. Movements shall not result in the track geometry being outside the limits as specified in RailCorp Engineering Standard ESC 210 - Track Geometry and Stability . The design shall provide for construction, expansion and contraction joints as appropriate.

5.6

Drainage Provision must be made for adequate surface drainage by efficiently directing water into the track drainage system. The track drainage system shall be cleanable as specified in RailCorp Engineering Standard ESC 420 - Track Drainage . Baseplates and fastenings must remain above water at all times. Ponding must not occur on slabs or in the void beneath any floating slab. The drainage design shall ensure that depth of run-off water on track slabs does not interfere with signalling and electrical equipment.

5.7

Track Interface

5.7.1

General The design of the track slab shall take of account of the interaction with the track including longitudinal effects, thermal effects, concrete shrinkage and traction/braking loads. The design shall consider the effect on both the track and the track slab, including interaction of slab expansion and rail expansion.





ESC 362

Track fastenings shall be approved resilient fastenings in accordance with RailCorp Engineering Specifications SPC 234 - Resilient Fastenings and SPC 235 - Resilient Baseplates. Where epoxy grouts are used under the rail seat pad, the minimum thickness of the pad shall be 7.5 mm.

5.7.2

Slab Constr ucti on Where rails are to be fixed to the completed slab, the finished surface of the slab shall be constructed to a tolerance of + 0 mm, - 5 mm from the design level. Where top down construction is used, the construction method shall ensure track fastenings are fully supported with no voids under the track fastenings. This is especially important on superelevated track.

5.7.3

Turnouts Where turnouts are planned in the track slab, full base plate fixings shall be installed to allow installation of the turnout. The rail must be straight railed through the turnout location without joints.

5.7.4

Guard Rails

5.7.4.1

General Guard rails may be required to be provided along track slabs where it is determined to be appropriate for providing protection to adjacent structures. Concrete upstands may be provided as an alternative to standard guard rail sections. Upstands are to be installed in the four foot, not on the outside of the track. The upstands shall be designed for a 80 kN lateral load. Guard rail installations are to comply with the following requirements: • •

•

•

•

•

•

•

•

•

•


Guard rail shall be new rail or recycled rail Category 1 (White rail). Guard rail section is to be the same as the running rail or one section size less than the running rail. Top of guard rail is to be no higher than the adjacent running rail and no more than 50 mm below the running rail. Each guard rail is to be plated and fastened on both sides at the same spacing as the running rail fasteners. Guard rails are to extend parallel for a minimum 20 metres in advance of the area being protected on the train approach side. Guard rails are to extend parallel for a minimum of 3 metres beyond the area being protected on the train departure side. A tapered nose section (“vee”), minimum 3.6 metres long, is to be installed on the train approach side of the guard rail. The design of the vee shall be in accordance with Drawing Number 785-570. The nose of the vee shall be bolted. Where rail traffic is bi-directional, the guard rail is to extend 20 metres beyond the area being protected on both approach and departure sides. Where traffic is bi-directional, the tapered nose section is to be installed on both ends of the guard rails. Clearance between gauge face of running rail and adjacent face of guard rail is to be 380 mm. Block-out holes for guard rail fastenings in concrete sleepers/slab shall be grouted with a high strength grout.




ESC 362

For fixing details, dimensional set-out and componentry detail and sizes, standard guard rail drawings are available:

5.7.4.2

785-568

Bridge guard rails Ballast top bridge Arrangement for concrete sleepered track

785-569

Bridge guard rails Details of concrete guard rail sleepers Concrete sleepered track

785-570

Bridge guard rails Ballast / Transom top bridge Arrangement for timber sleepered track

785-571

Bridge guard rails Timber sleepered track Details of special plating for tapered nose

Signall ing Interf ace Suitable isolation arrangements are to be made, where required, in track circuited and electrified areas. The tapered nose section (“Vee”) is to be insulated with an approved component - refer to Figure 1. This insulation requirement applies to new installations and where refurbishment of the guard rails is undertaken.

Figure 1 Where guard rails exceed 50 metres in length, additional insulation and bonding arrangements may be required. Design drawings are to specify that insulation and bonding arrangements shall be in accordance with the requirements of the Chief Engineer Signals. See RailCorp Engineering Standard ESG 100.17 - Signal Design Principles Track Circuits.





5.8

ESC 362

Noise and Vibratio n Track slabs shall be designed and constructed to attenuate the levels of vibration and regenerated noise in adjoining properties and structures, to the limits specified for the particular location or project and to comply with RailCorp’s environmental standards. Where floating track slabs are used to mitigate noise and vibration effects, they shall be of proven design with demonstrated performance in operating environments similar to the RailCorp network. The design shall take into account flexural vibration and noise radiation. The design shall provide for ease of access for inspection and maintenance of all track slab components. Operational rail vibration arises at the wheel/rail interface and propagates via the track support system to the tunnel structure, the ground and surrounding buildings. Occupants of nearby buildings may detect “rumble” noise during the passage of trains, called ground-borne noise. In some cases, occupants may directly perceive vibration, called ground-borne vibration. The operation of highly sensitive medical or scientific equipment can also be affected by vibration. Ground-borne noise and vibration are highly complex issues. ISO 14387-1 - Mechanical vibration – Ground-borne noise and vibration arising from rail systems – Part 1: General guidance provides general guidance on prediction and design methods. Where assessment and mitigation of ground-borne noise and vibration is required, methodologies shall be consistent with those defined in ISO 14387-1. The Interim Guideline for the Assessment of Noise from Rail Infrastructure Projects published by the New South Wales Department of Environment & Climate Change provides guidance on ground-borne noise goals. Ground-borne noise and vibration is likely to have a significant bearing on the tunnel alignment and/or track design. It is also important to consider operational and maintenance issues that may influence ground-borne noise and vibration from tunnels, including: •

• •

Track design features such as curves and crossovers, which increase the levels of ground-borne vibration generated at source, Ongoing maintenance of rolling stock, particularly wheels, and Ongoing maintenance of track, particularly the rail running surface.

Source vibration levels are dependent on the dynamic interaction of the train with the track support system. It is possible to vary the vibration spectrum generated at source by varying the track support stiffness. Reduction in the track support stiffness results in a reduction in source vibration and a reduction in ground-borne noise and vibration in surrounding buildings. However, the effect of varying track support stiffness actually has a frequency-dependent (“tuning”) effect. While there may be vibration reductions at most frequencies, a reduction in track support stiffness actually results in an increase in vibration at certain low frequencies. In other words, “tuning” of the track support system results in redistribution of vibration energy from one part of the frequency spectrum to another. The selection and design of such track support systems for ground-borne noise and vibration control requires careful consideration of maintenance and performance aspects. Particular consideration shall be given to: •

•


Modes of vibration of floating slab elements which may lead to a significant increase in low frequency radiated noise Transitions between track sections with differing support stiffness characteristics




• •

5.9

ESC 362

Wheel / rail interface issues such as corrugation development Access and inspection and maintenance of resilient components.

Transit ion Sectio n Trackfo rms Transition section trackforms must be provided in locations where two differing trackforms abut. The transition section must be designed to: • •

•

• •

Provide a progressive change in track stiffness; Provide an easily maintained trackform transition, which will not be prone to differential settlement; Provide accurate matching of track alignment under all load conditions, in order to avoid stress concentrations in components or uneven ride characteristics; Achieve the nominated levels of vibration and regenerated noise attenuation; Minimise the number of transition sections.

Where track slabs abut ballasted track, a transition slab must be provided to achieve a progressive change in track stiffness. The ballasted track on the transition slab shall be designed and installed in accordance with RailCorp’s track engineering standards. The minimum length of transition section trackform shall be 4.5 m. Transition section trackforms shall be designed for the same loads as the track slab.

6

Prohibited Configurations The following track slab configurations are prohibited: •


Embedded rail systems.



Engineering Standard - Track Slab -NSW

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