Civil Engineering Reference
In-Depth Information
extrapolating between the curves for an
N
1
value of 7.7, the volumetric strain is equal to 4.1
percent. Since the in situ liquefied soil layer is 1.0 m thick, the ground surface settlement
of the liquefied soil is equal to
v
4.1
____
____
Settlement
100
(
H
)
100
(1.0 m)
0.041 m
4.1 cm
Solution using Fig. 7.2:
The cyclic stress ratio from Eq. (6.6) is equal to 0.34, and the
calculated value of (
N
1
)
60
determined at a depth of 3 m below ground surface is equal to 7.7.
Entering Fig. 7.2 with CSR
0.34 and (
N
1
)
60
7.7, the volumetric strain is equal to 3.0
percent. Since the in situ liquefied soil layer is 1.0 m thick, the ground surface settlement
of the liquefied soil is equal to
v
3.0
____
____
Settlement
100
(
H
)
100
(1.0 m)
0.030 m
3.0 cm
Summary:
Since the soil is essentially a clean sand, the answers are identical to the
example problem in Sec. 7.2.2.
7.9
Solution using Fig. 7.1:
Since the soil has 96 percent fines, use the correction in
Sec. 7.2.2. Using the value for 75 percent fines,
N
corr
5. Therefore, (
N
1
)
60
for Fig. 7.1 is
(
N
1
)
60
N
corr
7.7
5
13. Assume that the Japanese
N
1
value is approximately equal to
this (
N
1
)
60
value, or use a Japanese
N
1
value of 13. For FS
0.53 and a Japanese
N
1
value
of 13, the volumetric strain
v
is equal to 3.0 percent. Since the in situ soil layer is 1.0 m
thick, the ground surface settlement of this soil layer is equal to
v
3.0
____
____
Settlement
100
(
H
)
100
(1.0 m)
0.030 m
3.0 cm
Solution using Fig. 7.2:
Since the soil has 96 percent fines, use the correction in Sec.
7.2.2. Using the value for 75 percent fines,
N
corr
5. Therefore, (
N
1
)
60
for Fig. 7.2 is (
N
1
)
60
N
corr
7.7
5
13. The cyclic stress ratio from Eq. (6.6) is equal to 0.34. Entering
Fig. 7.2 with CSR
0.34 and (
N
1
)
60
13, the volumetric strain is equal to 2.3 percent.
Since the in situ soil layer is 1.0 m thick, the ground surface settlement of this soil layer is
equal to
v
2.3
____
____
Settlement
100
(
H
)
100
(1.0 m)
0.023 m
2.3 cm
7.10
Solution using Fig. 7.1:
First determine the factor of safety against liquefaction
using Fig. 6.6, or
Layer depth, m
CSR
CRR (Fig. 6.6)
FS
CRR/CSR
2-3
0.18
0.11
0.61
3-5
0.20
0.06
0.30
5-7
0.22
0.08
0.36
