Civil Engineering Reference
In-Depth Information
T
2 m
(distance from pile tips to top of liquefied soil layer)
P
50 MN
5
10
4
kN
f
k
0
v
0
tan
Average depth
16 m, and use
t
18.3 kN/m
3
and
b
9.7 kN/m
3
. At 18 m,
v
0
1.5(18.3)
(16
1.5)(9.7)
168 kPa
168 kN/m
2
.
f
0.6 (168 kN/m
2
) (tan 34°)
68 kN/m
2
FS
2 (25 m
25 m) (2 m) (68 kN/m
2
)
_____________________________
5
10
4
kN
0.27
Therefore, the pile foundation will punch down into the liquefied soil layer located at a
depth of 17 to 20 m below ground surface.
8.12
Strip footing using Terzaghi bearing capacity equation:
e
0.10 m
(for middle third of footing,
e
cannot exceed 0.17 m, so
e
is within
middle third of footing)
T
2.5 m
(total thickness of unliquefiable soil layer minus footing
embedment depth
3
0.5
2.5 m)
c
1
s
u
50 kPa
50 kN/m
2
(upper cohesive soil layer)
c
2
0 kPa
0 kN/m
2
(liquefied soil layer)
B
1 m
N
c
5.5
(using Fig. 8.8 with
T
B
2.5
1.0
2.5 and
c
2
c
1
0)
Using the Terzaghi bearing capacity equation to calculate
q
ult
gives
q
ult
cN
c
s
u
N
c
(50 kN/m
2
) (5.5)
275 kN/m
2
FS
q
ult
q
so
q
275 kN/m
2
_________
55
kN/m
2
5
Q
(
B
6
e
)
_________
q
B
2
Q
[1
6(0.1)]
____________
55 kN/m
2
1
2
Q
34 kN/m
M
__
e
Q
M
eQ
0.1 (34)
3.4 kN
m/m
Strip footing using Fig. 8.9:
B
B
2
e
1
2(0.10)
0.8 m
