Civil Engineering Reference
In-Depth Information
For FS
1.0:
3.4 (29 m)
[750 cos 18°
F
h
(750) (sin 18°)
(2.4) (29)] (tan 29°)
__________________________________________________________
FS
1.0
750 sin 18°
F
h
(750 cos 18°)
Solving the above equation for
k
h
,
therefore for FS
1, gives
k
h
a
y
g
0.266. Per
the problem statement,
a
max
0.50
g.
Therefore,
a
y
a
max
0.266
g
0.50
g
0.532. Using
Eq. (9.3) with
a
y
a
max
0.532 gives
2.53
1
a
y
a
y
1.09
____
____
log
d
0.90
log
a
max
a
max
0.90
log [(1
0.532)
2.53
(0.532)
1.09
]
0.90
0.54
0.36
Solving for
d
gives
d
2.3 cm.
9.8
Slope height
9 m
1.5 m
10.5 m.
Consider possible liquefaction of the soil from ground surface to a depth of 10.5 m.
Based on the table shown below, the portion of the riverbank that has a factor of safety
against liquefaction
1.0 is from a depth of 2 m to the toe of the slope (11.5 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 susceptible to
failure, a mass liquefaction flow slide can be expected during the earthquake.
Depth,
D
r
,
percent
K
FS
FS
m
(
N
1
)
60
(see Note 1)
(see Note 2)
(see Note 3)
(see Note 4)
1.5
11
47
1.0
1.18
1.18
2.5
6.2
37
0.4
0.55
0.22
3.5
4.4
31
0.2
0.35
0.07
4.5
5.7
36
0.3
0.40
0.12
5.5
9.5
44
0.9
0.72
0.65
6.5
11
47
1.0
0.76
0.76
7.5
12
49
1.0
0.82
0.82
8.5
11
47
1.0
0.75
0.75
9.5
14
53
1.0
1.00
1.00
10.5
10
45
1.0
0.69
0.69
Notes:
1.
D
r
is based on (
N
1
)
60
correlation in Table 5.3.
2.
K
1
based on suggested guidelines in Sec. 9.4.2 and Fig. 9.24. For a 3:1 (horizontal:vertical) slope,
3
0.33.
3. Factor of safety against liquefaction for level-ground site (see Prob. 6.12).
4. Factor of safety against liquefaction for the 3:1 sloping riverbank, or FS for sloping ground
(FS for level
ground)(
K
).
