Deep Foundation

Deep Foundation
Deign Methods
Pile Selection
Guide
1
Ultimate Pile Load Capacity
Shaft Resistance
2
Shaft Capacity in Clay
(Alpha Method)
Shaft Capacity in Clay
(Alpha Method)
3
Shaft Capacity in Clay
(Alpha Method)
Soft-stiff clay
Adhesion
factors
4
© 2004 Brooks/Cole Publishing / Thomson Learning™
© 2004 Brooks/Cole Publishing / Thomson Learning™
Nature of variation of undrained shear strength (cu) with time around a pile
driven into soft clay
Variation of Qs with time for a pile driven into soft clay
(based on load test results of Terzaghi and Peck, 1967)
5
© 2004 Brooks/Cole Publishing / Thomson Learning™
Compaction of sand near driven piles
(after Meyerhof, 1961)
= pile critical depth
© 2004 Brooks/Cole Publishing / Thomson Learning™
Unit frictional resistance for piles in sand
6
• For z = 0 to L’
fs = Kσo’tanδ =βtanδ
Where β = Kσo’
• For z = L’ to L
fs = fz=L
Qs = fs Σp ΔL
Where
p = perimeter of pile
ΔL = incremental pile length which p and fs
are taken constant
Shaft Capacity in Sand
(Beta Method)
δ is the shaft soil friction angle
7
Shaft Capacity in Sand
(Beta Method)
Shaft Capacity in Sand
(Beta Method)
8
Vesic Tests
Shaft Capacity in Sand
(Practical Design)
9
Shaft Resistance
End Bearing
10
End Bearing Failure
Assumptions
End Bearing
Failure
Assumptions
11
End Bearing Factor (Nq)
End Bearing based on SPT
12
End Bearing Layered Soils
End Bearing Issues
13
Cone Penetration Test (cpt)
Shaft Resistance in Clays
14
Shaft Resistance in SAND
Beware of variability with
different methods
End Bearing
15
Piles to Rock
Piles to Rock
16
Importance of Shaft Friction
Piles to Rock
a, b reduction factors
(Williams & Pells 1981)
17
Piles to Rock
End Bearing Parameters
Uplift Capacity
18
Uplift Capacity SAND
Uplift Capacity SAND
Single Pile
19
Cyclic Loading
Cyclic Stability Diagram
20
Negative Skin Friction
Down drag due to settlement
© 2004 Brooks/Cole Publishing / Thomson Learning™
21
© 2004 Brooks/Cole Publishing / Thomson Learning™
Negative skin friction on a pile in the harbor of
Oslo, Norway
Pile Groups
© 2004 Brooks/Cole Publishing / Thomson Learning™
(based on Bjerrum et al. (1969) and Wong and Teh (1995)
22
© 2004 Brooks/Cole Publishing / Thomson Learning™
Pile Group Efficiency
23
Friction Pile Groups in Clay
24
© 2004 Brooks/Cole Publishing / Thomson Learning™
© 2004 Brooks/Cole Publishing / Thomson Learning™
Block Analysis
© 2004 Brooks/Cole Publishing / Thomson Learning™
25
© 2004 Brooks/Cole Publishing / Thomson Learning™
© 2004 Brooks/Cole Publishing / Thomson Learning™
26
Other Pile Group Cases
Effect of Weak Under Layer
27
Pile Structural Design
Buckling
28
Buckling
Corrosion Rates for Steel
29
Corrosion Protection Methods
30