Presentation by by Sandeep Sandeep Pattiwar, TANGENT Technical Solutions to Power Grid Corporation of of India India Limited, Gurgaon Date: 8th February February 2010 2010
Well Foundations in India Introduction
In large parts of of India, India, well well foundations are commonly Design and construction practices have been ‐ loads and foundation depths , increases. For Second Hooghly Hooghly Bridge, Bridge, 24 m di diaa well llss . constructed in India is up to 70 m below below WL WL
Well Foundations in India Introduction
In large parts of of India, India, well well foundations are commonly Design and construction practices have been ‐ loads and foundation depths , increases. For Second Hooghly Hooghly Bridge, Bridge, 24 m di diaa well llss . constructed in India is up to 70 m below below WL WL
Well Foundations in India Introduction
Daring efforts are on in different parts of the of the world world to Even bridges between continents are in process, ‐ ‐ , In India hundreds of thousands of thousands of bridges of bridges have been During the first decade of this of this century, about s.100,000 cr are expec e o e spen on r ges Foundations cost 50 % or more
Use of Well Foundation Introduction
Past Experience making it more reliable and
Well foundations are more suitable for deep water
like River/Creek Bridges , Deep foundation and suitable for alluvial soil which ma n y cons s o an y No special equipment and heavy machineries are requ re
Use of Well Foundation Introduction
Used in India and Indian Sub‐continent only e oun at on s pre era e to p e oun at on t has to resist large horizontal forces e oun at on s more su ta e or eep water w ere it is difficult to carry construction equipment e oun at on s meant or eep oun at on w ere the river bed gets scoured and forces need to be rans erre o eeper eve .
Pile Foundation Vs Well Foundation Item
Pile Foundation
Well Foundation
Vertical Capacity
By Side Friction as well End Bearing
Only End Bearing
Lateral Capacity
By Fixity Depth in clay as Net balance of Passive well Sandy Soil, alternatively Resistance and Active Spring Analogy can be used
Structure
Slender and Flexible
Short and Rigid
Construction Equipment
Heavy and Costly like Rig and latform
Crane and Grab
Time
Faster
Longer
Protection
Liner is re uired u to scour level
Caisson is re uired if necessary for construction requirement
Shapes and Sizes Shape is governed by the requirement of stability during
Need for effective streamline flow
D‐Shape well for wider and heavy foundations
functionality Circular diameter is u to 12 m without an dia hra m else either diaphragm is provided or extensive study is undertaken for the steining stresses.
Shapes and Sizes
Shape is governed by the requirement of stability during
Dredge hole for easy dredging > 2 m
D‐Shape well is not to have
Well Foundation A Well foundation consist of following components:
Cutting Edge e ur Bottom Plug
Sand Filling
Intermediate Plug Well a
Input Data
Forces above well foundation , velocity and Discharge
Bore Hole details for assessing depth of soil and rock, if an Geo‐technical Investigations including stratification, density, φ and c and weighted mean diameter of bed material Bearing Capacity
Special Requirement
Variation of depth of water i.e. HFL and LWL
Working Months availability
Any other feature depending on the location like rock , environment condition Pneumatic Sinkin in case of dee er foundin level with boulder strata Floatin caisson incase of deep standin water
Depth of Well Foundation for Soil
Mean scour depth is calculated as per bed material 1 / 3
d sm
= 1.34⎜⎜ ⎟⎟ ⎝ k sf ⎠
This “mean scour depth” is used to calculate Maximum scour depth to account local scour effect
Db
For Pier foundations : 2 x dsm from HFL For Abutment foundations: 1.27 x dsm from HFL
Grip Length: The minimum depth of foundation below scour level is 1/3 rd of Maximum Scour Depth
Depth of Well Foundation for Rock
The well foundation shall be taken up to sound rock pneumatic sinking, if required.
depth of 300 mm in hard rock and 600 mm in soft . Diameter of shear key must be minimum 1.5 m or 1.5 m . . 6 dowel bars of 25 mm diameter with anchored 1.5 m . .
Well Steining Thickness of well steining is governed by following
Natural sinking or sinking without excessive kentledge
tilt and shift Hoo com ression for the differential ressure durin construction and service Hoop tension arising out of differential earth pressure developed during sand blow Structural design at all levels due to external forces
Well Steining factors:
The thickness arrived for self sinking, empirically: h = kd l Where k is a constant and depends on the type of well ste n ng In Cement Concrete 0.03 Twin D
wells
0.039
d is diameter of well or smaller dimensions in D‐ Well l is depth of well below top of well or LWL, which ever is higher
Well Steining of soil stratum:
Well Steining
Steining thickness can , height of well is more . , the reduced diameter of well should be able to support structure above well foundation.
Well Steining – Structural Design
Plain Concrete Wells
er ca e n orcemen = 0.12 o ross rea Horizontal Hoop Reinforcement = 0.04% of volume
oncrete
e s
Vertical Reinforcement = 0.2% of Gross Area Inner Face, vertical reinforcement = 0.06% Transverse Reinforcement as per column design and s a not e ess t an 0.04 o vo ume
Well Steining – Structural Design
Checking of steining stresses at all critical sections and
Well cap bottom level e eve o c ange n s e n ng c ness Below scour level where resultant shear is zero
Well steining also shall be checked for ovalisation momen s
– •
As per ‐IRC‐78‐2000 C ause‐708.2.3.5 If Specialised methiods of sinking such as jackdown method are adopted then the steining thickness may be adjusted according to design and construction requ rements.
Check for cohesion‐less soil
IRC 45 recommends checking of well
Side Earth Resistance
Theory:
Side Earth Resistance
In case of c‐φ soil, effect of ‘c’ may be added as per
Bell Correction
Side Earth Resistance – F.O.S.
The Side earth resistance for pier wells is considered The resistance calculated is ultimate and converted . . . Net pressure of Passive and Active is calculated
. . . s cons ere 2 or oa com nat on w t out wind or seismic . . . s cons ere 1. or oa com na on w w n or seismic
Side Earth Resistance
For cohesionless soil, IRC 45 may be used for pier well
Side earth resistance may be ignored in case of
However, side resistance of well foundations resting on than 100 t/m2
Tilt and Shift
In Design of well, tilt of 1 in 80 and shift of 150 mm due cause most severe effects shall be considered If the actual tilt and shift exceeds the above limits remedial measures have to be resorted to bring the well within limit. However, if not possible then its effect on bearing pressure, steining stresses shall be examined and if pressure.
Cutting Edge
To penetrate easily through the different type of strata . designed to cater resistance which encountered during . . Guidelines of IRC 78 stipulate that its weight should . When there are partitions, the intermediate cutting cutting edge to prevent rocking.
Cutting Edge
Cutting Edge
Cuttin Ed e
Cutting Edge
Required 40 kg/meter
Well Curb
Minimum resistance while being sunk. trong enoug to transm t orces rom ste n ng to t e bottom plug Internal angle of curb shall be kept in between 30 degree to 7 de ree.
Well Curb
Well Curb
Well Curb
Bottom Plug
Is provided to transfer the load from steining to underneath strata. cutting edge. , faces have been cleared thoroughly.
Bottom Plug
FILLING
Bottom Plug
Well Cap
The bottom of well cap shall be as low as possible . Well cap design is as per any rational method orma y es gn s cater to cons er part a x ty at t e junction to take care large fixity moments.
Filling
Filling if required shall be sand or excavated material . Incase filling is not done, bottom plug shall be . Normally, if vertical pressure is within limit, filling is . In a high seismic area, filling is avoided above scour eve .
Construction of Well Foundations:
Conventional Construction on Land / Sand Islands
Floating Caissons
Jack down method
neuma c
n ng
Conventional Construction on Land / Sand Island Method
Well Sinking – Sand Island Method
Well Sinking – Sand Island Method
Well Sinking – Sand Island Method
GANGA BRIDGE AT PATNA
Floatin Caisson
Area for fabrication of steel caisson will be made near the river bank by constructing suitable cofferdam
nta t o stee ca sson w e a r cate on a leveled ground in fabrication yard Gra ing o soil rom within and around the caisson will be carried out so as to allow the water . caisson will be held in position with proper guying
The caisson will be towed to the desired location and aligned properly Caisson will be held in position with tethering arrangement Concrete quantity as per design requirements will be poured evenly in the curb portion so that the ca sson gets urt er mmerse n t e water Next lift of steel caisson will be built and concrete quant ty o es gne amount w e poure ns e the caisson
This procedure will continue till the cutting edge comes near e r ver e
When the caisson is about to get grounded its alignment will be rechecked
Water will be poured inside the caisson to ensure its grounding at exact location
Wate aterr ballas ballastt will will be re lac laced ed with with conc concret retee so that that caisson gets grounded at its exact location the well will be taken to its founding level level as per
Tethering arrangement General Details
Caisson Aligned at location
First lift of concrete poured
Shifting of concrete over Bar e
Concrete placing
Build next lift of Caisson And place concrete
Checking of alignment with water ballast
Muck removal by grabbing
Sinking in progress
Steining Concreting & sinking
Sinking in progress
Final stage – At founding level
Well Caisson Launching
Caisson Fabrication Yard
Launching of Caisson
Well Caisson Launching
to location
Sinking in progress
SECOND HOOGHLY BRIDGE Enabling works for caisson sinking
JOGIGOPHA BRIDGE
Jogighopa Bridge
Jogighopa Bridge
Floatin Caisson bein Towed to Location
Well Sinking By Jack Down Method
Well Sinking By Jack Down Method
Well Sinking By Jack Down Method
Well Sinking By Jack Down Method
Pneumatic sinking is resorted to when open sinking can not be continued in hard strata and excavation by open grabbing and chiseling is not possible. When neumatic sinkin is ado ted it is ossible to inspect the well from inside and take the decision based on the actual conditions.
Pneumatic Sinking
• •
In this method airtight cover is fixed on dredge hole and compressed air is pumped in, so that water is pushed out of well up to cutting edge level. Men are sent inside to carryout manual excavation. Muck is removed through shaft without releasing pressure. . . .Contd.
Arrangement for Pneumatic Sinking
Kali Bridge – Pneumatic Sinking
Kali Bridge – Pneumatic Sinking
Limitations only when the well can not be founded safely with . , which depends upon the depth of cutting edge below .
without undue risk to human lives is restricted to . ….contd
Limitations • Man feels increased pressure on ear drum when inside
. in sever pain, bleeding and may cause damage to ear drum. • Dizziness, double vision, incoherence of speech are
quite common and some times man becomes unconscious after coming out of well.
...
Limitations • Due to the physiological effects on men working inside
, restricted to about two hours. This is followed by period of 5 to 6 hours
CASE STUDY Second Hooghly Bridge
Second Hooghly Bridge
Second Hooghly Bridge
Second Hoo hl Brid e
Second Hooghly Bridge , Calcutta
Second Hooghly Bridge , Calcutta
SECOND HOOGHLY BRIDGE
,
Sinking a Pylon caisso
11
CASE STUDY Jogighopa Bridge
Jo i ho a Brid e
Brahmaputra Bridge, Jogighopa, 2.28 km
Wells 7 and 13 tilted; more than a year to correct e s 17 1 on ar roc at steep nc ne 1:1 . 12 x 1500 mm dia anchor piles, provided through steining, For well 17 additional 1500 dia, 8 nos, external piles , Two rows of jet grouted piles around periphery of the s e n ng as cur a n wa
Brahmaputra Bridge, Jogighopa WELL CAP
∅ 1.5 m
. 1.5 m
50 m 2.5 m RC PLUG
DRILL PIPE WITH AIR CONTROL VALVES WORKING PLAT WORKING PLATFORM FORM CASING
m
DRILL PIPE STABILIZER
PLAN
+ 35.00 m CAISSON STEINING AIR - LIFT DRILL DRILL PIPES PIPES
CC PLUG
HEAVY DUTY STIFF ASSEMBLY HEAVY DUTY STABILIZER
3m
STIFF SPACER PIPE
∅ 1.5 m
PILE
NON ROTATING DRUM STABILIZER - 12 12.5 .50 0m
m
FIG. SECTION
JOGIGHOPA BR. FOUNDATIONS
DRILL BIT
WIRTH DRILLING RIG
Jogi Jogigh ghopa opa Bridg Bridge e – Caisson Fabrication
JOGIGOPHA BRIDGE pway or
oat ng
a ssons
Jogighopa Bridge
Jogighopa Bridge Handling Caissons
Jogighopa Bridge
Jet Grouting
Design & construction of a ove oun at ons, were governed by following main (i) Likely scour upto rock strata. (ii) Uniform support over steeply sloping strata (iii) Sinking under pneumatic condition was not feasible
Foundation scheme for wells 17 n ew o a ove, o ow ng an 1 scheme was adopted :
(i) Sink well upto one metre
above top of rock strata. ta se so aroun we curb above rock strata by . (iii) Support steining by constructin six out of twelve 1.5 m diameter RC piles through 1.65 m steining, with 10 m anchor len th in rock strata.
Foundation scheme for wells 17 and (iv) Remove sand in dredge‐hole y gra ing an air‐ i ting to clean entire area includin that below well curb. (v) Construct concrete bottom . (vi) Construct balance six piles to complete anchoring of . (vii) Construct RC plug over the bottom plug in dry condition after dewatering the well.
Jogighopa Bridge - Piling
Piling through the Well Foundation
CASE STUDY Nepal Bridge
Artesian Conditions Shivganga bridge, Nepal, 8 spans x 32 m
Artesian head encountered at 17 m below GL e re es gne w t oun at on rest ng on c ay a ove the artesian layer. Plus bed protection :
pstream ownstream aprons Concrete floor
ut‐o wa s,
Artesian Conditions - Khara Bridge, Nepal Artesian Bubbles
SAR 6 Y2k
CASE STUDY Passighat Bridge
Passighat Bridge, Arunachal Pradesh Well Foundation
Non availability of formula for scour depth in bouldary Subsoil with large boulders 2 to 3 m dia; rate of sinking 10 to 20 mm er hour initiall Sinking very difficult due to large size boulders; considerable slow down in overall progress Difficulties in finally deciding the foundation level; decision making body in considerable dilemma ‐R K Dhiman IABSE colloquium 1999 foundations for major
bridges
Passighat Bridge, Arunachal Pradesh Well Foundation
Design consultant recommended 50 m deep wells e ore ata n cate ar cong omerate r g t through the depth up to 50 m except top 10 m ore recovery was c ose to 90 During execution, impossible to sink the well beyond 10 m w t convent ona met o Pneumatic sinking used up to 30 m; beyond that it is not possi e p ysio ogica y to wor un er compresse air, it is not permitted as per code
Well Foundation Delays ass g a
r ge, runac a
ra es ,
Started in 1987 and well Design envisaged, 50 m dee wells. Hard conglomerate strata with very large boulders did not perm t s n ng After 15 years of struggle sinking, the founding level was raised b 22 m.
Boulder dredged during s n ng
m ong
Unsuitable foundation design ou er dred ed during sinking SAR 6 Y2k
g:
: LEGEND
Constructability
Narmada bridge, Chandod water
Bridge in Nepal
SAR 6 Y2k
Batching Plant on Shore
4/2/2010
Floating Batching Plant
Concrete cofferdam being towed to location
Cranes for Concreting and Dredging
4/2/2010
Floating arrangement for Batching Plant Concrete pump and placer boom
GANGA BRIDGE AT PATNA oat ng crane or we s n ng
Well sinking by cranes and grabs
SECOND HOOGHLY BRIDGE Enabling works for caisson sinking
Well sinking ;Tilt correction Kentledge for Well Sinking
e s n ng ;
correc on
Tilt Rectification of Wells Ti t Recti ication o We s
Tilt Rectification of Wells
Tilt Rectification Platform for Well Foundation
Tilt Rectification Platform for Well Foundation
4/2/2010
Kan Ka ndroo droorr Br Brid idg ge ac across ross Sut Sutle lejj - Ba Badl dly y t te we e ng correcte
SAR 6 Y2k
Kandroor Bridge
SAR 6 Y2k
Foundation Problems
IRC IRC Paper 253 ‐ Rupnarayan Bridge, West Bridge, West Bengal 293 ‐ asse n ree r ge, uma 314 ‐ Godavari Bridge, Maharashtra
32 ‐ a a r ge, 359 ‐ Haldi Bridge, WB Bridge, WB 400 ‐ Hasdeo Bridge, Champa, MP 434 ‐ Tapi Bridge, Idgaon, Maharashtra 464 – Kalyani Bridge, WB Bridge, WB Indian Hi hwa s Dec Dec 1 82 Ar un Khola Brid e Ne al
Conclusion
The construction of wells have not always been smoo , a var e y o pro ems ur ng cons ruc on as resulted in inordinate delays, increased cost of rect cat on an even a an onment o we s With advance methods of geo‐technical investigation, equipments, revised codal specifications and sound engineering practices, we should able to decide the methodology and foundation type in advance.