Civil Engineering Reference
In-Depth Information
Glacial clay:
γ
=
20 kN/m
3
c
u
at 7.0 m
=
120 kPa
c
u
at 8.0 m
=
145 kPa
c
u
at 11.0 m
=
220 kPa
adhesion factor,
α
=
0.6
N
c
=
9.0
Determine the ultimate bearing capacity of the pile for:
a) embedded length
=
8 m
b) embedded length
=
11 m
Solution:
Fill:
20 3 0
2
×
.
×
Q
=
A K
γ
z
tan
δ
= × × × ×
(
π
0 5 3
.
)
1 0
.
tan(
0 75 30 )
.
× °
=
58 6 kN
.
s
s
s
Gravel:
21 4 0
2
×
.
×
Q
=
A K
γ
z
tan
δ
= × × ×
(
π
0 5 4
.
)
2 0
.
×
60
+
tan(
0 75 35
.
×
° =
)
632 1
. kN
s
s
s
Clay (length
=
8 m):
120 145
2
+
× × ×
Q
= × × =
α
c A
0 6
.
×
(
π
0 5 1 0
.
.
)
=
124 9
.
kN
s
u
s
2
0 5
4
.
=
Q
c N A
145 9 0
.
256 2
.
kN
= × ×
=
×
× ×
π
b
b
c
b
Clay (length
=
11 m):
120
+
220
× × ×
Q
= × × =
α
c A
0 6
.
×
(
π
0 5 4 0
.
.
)
=
640 9
.
kN
s
u
s
2
0 5
4
.
2
=
Q
= × ×
c N A
=
220 9 0
×
.
× ×
π
388 8
.
kN
b
b
c
b
Ultimate bearing capacity:
Q
=
Q Q
+
u
b
s
a) 8 m: Q
u
=
256.2
+
(58.6
+
632.1
+
124.9)
=
1071.8 kN
b) 11 m: Q
u
=
388.8
+
(58.6
+
632.1
+
640.9)
=
1720.4 kN
10.5.3 Determination of soil piling parameters from in situ tests
With cohesionless soils it is possible to make reasonable estimates of the values of q
b
and f
s
from
in situ
penetration tests. Meyerhof (
1976
) suggests the following formulae to be used in conjunction with the
standard penetration test.
Driven piles
40
ND
B
Sands and gravel q
b
≈
≤
400 (
N kPa
)
