A Pile Design

7/28/2019 A Pile Design

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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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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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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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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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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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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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Documents

A Pile Design