1

Deep Foundation

Deign Methods

Pile SelectionGuide

2

Ultimate Pile Load Capacity

Shaft Resistance

3

Shaft Capacity in Clay(Alpha Method)

Shaft Capacity in Clay(Alpha Method)

4

Shaft Capacity in Clay(Alpha Method)

Soft-stiff clay Adhesion

factors

5

Nature of variation of undrained shear strength (cu) with time around a pile driven into soft clay

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Variation of Qs with time for a pile driven into soft clay(based on load test results of Terzaghi and Peck, 1967)

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Compaction of sand near driven piles (after Meyerhof, 1961)

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Unit frictional resistance for piles in sand© 2004 Brooks/Cole Publishing / Thomson Learning™

= pile critical depth

7

• For z = 0 to L’fs = Kσo’tanδ =βtanδ

Where β = Kσo’

• For z = L’ to Lfs = fz=L

Qs = fs Σp ΔLWherep = perimeter of pileΔL = incremental pile length which p and fs

are taken constant

Shaft Capacity in Sand(Beta Method)

δ is the shaft soil friction angle

8

Shaft Capacity in Sand(Beta Method)

Shaft Capacity in Sand(Beta Method)

9

Vesic Tests

Shaft Capacity in Sand(Practical Design)

10

Shaft Resistance

End Bearing

11

End Bearing Failure Assumptions

End Bearing Failure

Assumptions

12

End Bearing Factor (Nq)

End Bearing based on SPT

13

End Bearing Layered Soils

End Bearing Issues

14

Cone Penetration Test (cpt)

Shaft Resistance in Clays

15

Shaft Resistance in SAND

Beware of variability with different methods

End Bearing

16

Piles to Rock

Piles to Rock

17

Importance of Shaft Friction

Piles to Rocka, b reduction factors

(Williams & Pells 1981)

18

Piles to RockEnd Bearing Parameters

Uplift Capacity

19

Uplift Capacity SAND

Uplift Capacity SANDSingle Pile

20

Cyclic Loading

Cyclic Stability Diagram

21

Negative Skin Friction

© 2004 Brooks/Cole Publishing / Thomson Learning™

Down drag due to settlement

22

Negative skin friction on a pile in the harbor of Oslo, Norway

(based on Bjerrum et al. (1969) and Wong and Teh (1995)

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Pile Groups

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Pile Group Efficiency

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™Friction Pile Groups in Clay

25

Block Analysis

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© 2004 Brooks/Cole Publishing / Thomson Learning™

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27

Other Pile Group Cases

Effect of Weak Under Layer

28

Pile Structural Design

Buckling

29

Buckling

Corrosion Rates for Steel

30

Corrosion Protection Methods