a pile design
TRANSCRIPT
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RELEVENT STANDARDS
Manual on the Design andConstruction of well and pileFoundations issued by RDSO
IS 2911- Part I Section I Driven cast in situ piles
Section II- Bored cast in situ piles
Section III- Driven precast concretepiles
IS 2911- Part IV- Load test
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RELEVENT STANDARDS
Concrete Bridge code- Forstructural design
IRC- 78- For Road bridgefoundations, can be referred forguidance
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END BEARING PILE
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FRICTION PILES
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DRIVEN PILES
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BORED PILING
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STEPS OF DESIGN
1. From soil data, depth of scour fix length ofpile
2. Base on thumb rules, fix dia of pile3. Calculate load carrying capacity of single pile
using static formulae4. Do rough design for selected group of piles.
Spacing to be based on thumb rules5. Check design for load carrying capacity,
settlement, depth etc.
6. Revise design if required7. Conduct load test to confirm capacity of pile8. Do structural design
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BORED CAST IN SITUPILES ARE MOST COMMONFOR RAILWAY BRIDGES,SO FURTER DISCUSSIONIS FOR BORED CAST IN
SITU PILES ONLY
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IMP. CODAL PROVISIONS
DIA. OF PILE
Bridge Manual- > normally 1 m
IRC-78 Bored piles on land- min. 1 m
Bored pile in river bridge- min. 1.2 m
IS 2911- Part I, Section 2 Provisions are for max. dia of 2.5 m
For Railway bridges dia. Of 1 m to 1.5m be normally adopted
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IMP. CODAL PROVISIONS
SPACING OF PILE IRC-78
Friction- min. 3 D End bearing- Can be reduced to clear distance= D
that is c/c 2D
IS 2911- Part I, Section 2 End bearing- hard soil- Min. 2.5 D End bearing- hard rock- Min. 2.0 D Friction- Min 3.0 D
RDSO Manual Friction min. 3 D End bearing- Min. 2.5 D
Max. 4 D
For Railway bridges spacing of 2.5 D to 3.5Dbe normally adopted
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IMP. CODAL PROVISIONS
GROUP BEHAVIOR IRC-78
End bearing- If spacing > 2.5 D, no reduction
Friction- If spacing > 3 D, no reduction
Check for block failure
Settlement of group/single pile given for differentwidth of group/pile dia
IS 2911- Part I, Section 2 Bored piles- end bearing- No reduction
Other cases descriptive guidelines given
RDSO Manual Dense sand not underlying by weak soil driven
pile No reduction
Loose sand soil 50% reduction
Sand not underlying by weak soil bored-reduction 33%
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IMP. CODAL PROVISIONS
PILE CAP IRC-78
Min. thickness 0.6 m or 1.5 m whichever isless
Minimum offset of 150 mm beyond outer face
Pile to project 50 mm into pile cap IS 2911- Part I, Section 2
Offset of 100-150 mm beyond outer face Pile to project 50 mm into pile cap Should be rigid enough Can be designed by taking dispersion at 45
degrees both from substructure and pile uptocentre line
RDSO Manual NIL
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IMP. CODAL PROVISIONS
CONCRETE AND STEEL IRC-78
M 35, Min. cement 400 kg/m3, Max. W/C ratio 0.4,slump 50mm (150-200 for tremie)
Min. long reinforcement 0.4%, links min. 8 mm @150 mm c/c.
Min cover 75 mm. IS 2911- Part I, Section 2
M 20, Min. cement 400 kg/m3, 10% extra cementwhen under water, slump 100- 180 mm (150-180for tremie)
Min. long reinforcement 0.4%, Min. spacing100mm, links min 6 mm @ 150 mm c/c.
Min cover 40 mm. RDSO Manual
NIL CBC to be followed based on enviornmental
condition
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IMP. CODAL PROVISIONS
FOS IRC-78
2.5 if derived from static formulae for
soil. 5 for end bearing on rock and 10 forsocket resistance.
IS 2911- Part I, Section 2 Appendix given for calculating strength
with static formulae
RDSO Manual 3 if derived from static formulae.
2 if derived from load test
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Factor of safety
DEPENDS UPON Reliability of the soil parameters
Soil Type
Spatial variability of the Soil
Uniform orErratic
The soil exploration programme Average or Extensive
Method of construction, inspectionand quality control
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The factor of safety based on load Test
shall be increased in followingunfavorable conditions:-
a) Settlement is to be limited or unequalsettlement avoided
b) Large impact or vibrating loads areexpected
c) The properties of the soil are expected
to deteriorate with time The maximum permissible increase
over the safe load of a pile on accountof wind load is 25%
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ALIGNMENT CONTROL
For pile group_
FOR VERTICAL PILES A DEVIATION OFNOT MORE THAN 1.5 %
FOR RAKER PILES A DEVIATION OF NOT
MORE THAN 4 % PILE SHOULD NOT SHIFT MORE THAN 75
MM OR D/4 WHICHEVER IS LESS ( FORPILES LESS THAN OR EQUAL TO 600 MM
DIA. ) 75 MM OR D/10 WHICHEVER IS MORE
FOR PILES MORE THAN 600 MM. DIA.PILE
BORED CAST INSITU PILES
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LOAD CARRYING CAPACITY
APPENDIX B - sandy soil
Similar details for clayey soil is also there in APPENDIX B
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DEPTH OF FIXITY
Amendment 3 of IS code, Appendix C
Determine T
K1 given in table1, use submerged value varying from0.146 for loose sand to 1.245 for dense sand
Read L1/T v/s Lf/T fro fig 2
L1 is depth of scour Le should be more than 4R/4T
Calculate BM and shear forceafter applying correction factor as per fig. 3
Le
L1
Q
Lf
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DESIGN EXAMPLE
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References for further study
Theory & Practice of Foundation Design
by Som N.N. and Das S.C.
Foundation Design & Construction by
Tomlinson M.J.
Foundation Design Theory and Practice
by Coduto.
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