22
z, m
σ
v
, kPa
u, kPa
σ
'
v
, kPa
σ
'
h
, kPa
τ
, kPa
At the soil surface
0
0
0
0
0
0
At the water table
5
95
0
95
47.5
23.17
At the base of the pile
25
475
196.2
278.8
139.4
67.99
The surface area of the upper 5m of the pile is (
π
×
0.3)m
×
5m = 4.71m
2
,
and the average
shear stress over this area is 23.17kPa
÷
2 = 11.59kPa. The surface area of the lower 20m of
the pile is (
π
×
0.3)m
×
9m = 18.85m
2
,
and the average shear stress over this area is
(23.17kPa + 67.99kPa)
÷
2 = 45.58kPa. Thus the overall frictional resistance is
(4.71m
2
×
11.59kPa) + (18.85m
2
×
45.58kPa) =
914kN
Q2.6 The depth of the friction uplift pile described in main text Example 2.4 is increased to
20m, where the undrained shear strength of the clay is 40 kPa. Calculate the short and long
term uplift resistance of the 20m pile.
Q2.6 Solution
The total shear resistance of the clay/pile interface is given by
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 Fall '11
 StuartChalk
 Analytical Chemistry, Force, Geotechnical Engineering, Shear Stress, Shear strength

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