Civil Engineering Reference
In-Depth Information
9.9
Slope height
0.4 m
5 m
5.4 m.
Consider possible liquefaction of the soil from ground surface to a depth of 6.2 m.
Depth,
D
r
,
percent
K
FS
FS
m
(
N
1
)
60
(see Note 1)
(see Note 2)
(see Note 3)
(see Note 4)
1.2
7.7
40
0.8
0.56
0.45
2.2
9.0
43
0.9
0.59
0.53
3.2
6.5
38
0.7
0.39
0.27
4.2
10
45
1.0
0.61
0.61
5.2
8.2
41
0.8
0.50
0.40
6.2
15
55
1.0
0.89
0.89
Notes:
1.
D
r
is based on (
N
1
)
60
correlation in Table 5.3.
2.
K
based on suggested guidelines in Sec. 9.4.2 and Fig. 9.24. For a 4:1 (horizontal:vertical) slope,
1
4
0.25.
3. Factor of safety against liquefaction for level-ground site (see Prob. 6.15).
4. Factor of safety against liquefaction for the 4:1 sloping riverbank, i.e., FS for sloping ground
(FS for level
ground)(
K
).
Based on the above table, the portion of the riverbank that has a factor of safety against
liquefaction
1.0 is from a depth of 1.2 m to the toe of the slope (5.4 m below ground sur-
face). Thus most of the 4:1 sloping riverbank is expected to liquefy during the design earth-
quake. As indicated in Sec. 9.4.1, if most of the sloping mass is susceptible to failure, a
mass liquefaction flow slide can be expected during the earthquake.
9.10
Before improvement:
Slope height
0.5 m
5 m
5.5 m
Consider possible liquefaction of the soil from ground surface to a depth of 5.5 m.
Depth,
D
r
,
percent
K
FS
FS
m
(
N
1
)
60
(see Note 1)
(see Note 2)
(see Note 3)
(see Note 4)
0.5
39
85
1.0
2
2
1.5
19
63
1.0
0.66
0.66
2.5
13
51
1.0
0.43
0.43
3.5
14
53
1.0
0.42
0.42
4.5
23
69
1.0
0.76
0.76
5.5
12
49
1.0
0.36
0.36
Notes:
1.
D
r
is based on (
N
1
)
60
correlation in Table 5.3.
2.
K
based on suggested guidelines in Sec. 9.4.2 and Fig. 9.24. For a 3:1 (horizontal:vertical) slope,
1
3
0.33.
3. Factor of safety against liquefaction for level-ground site (see Prob. 6.18).
4. Factor of safety against liquefaction for the 3:1 sloping riverbank, i.e., FS for sloping ground
(FS for level
ground)(
K
).
Based on the above table, the portion of the riverbank that has a factor of safety
against liquefaction
1.0 is from a depth of 1 m to the toe of the slope (5.5 m below
ground surface). Thus most of the 3:1 sloping riverbank is expected to liquefy during
the design earthquake. As indicated in Sec. 9.4.1, if most of the sloping mass is suscep-
tible to failure, a mass liquefaction flow slide can be expected during the earthquake.
