Civil Engineering Reference
In-Depth Information
safety for overturning, and maximum pressure exerted by the base of the mechanically sta-
bilized earth retaining wall for static and earthquake conditions.
Answer:
Static conditions:
FS for sliding
1.73, FS for overturning
3.78, and maximum pressure
q
4300 lb
ft
2
.
Earthquake conditions: FS for sliding
1.29, FS for overturning
2.3, and
N
is not within
the middle third of the base of the wall.
10.8
Use the data from the example problem in Sec. 10.2.5, and assume that the ground
surface behind the mechanically stabilized earth retaining wall slopes upward at a 3:1 (hori-
zontal:vertical) slope inclination. Also assume that the 3:1 slope does not start at the upper
front corner of the rectangular reinforced soil mass (such as shown in Fig. 10.8), but instead
the 3:1 slope starts at the upper back corner of the rectangular reinforced soil mass. Calculate
the factor of safety for sliding, factor of safety for overturning, and maximum pressure exerted
by the retaining wall foundation for the static and earthquake conditions, using the equations
in Fig. 10.3.
Answer:
Static conditions: FS for sliding
1.60, FS for overturning
3.76, and
maximum pressure
q
4310 lb
ft
2
. Earthquake conditions: FS for sliding
0.81, FS for
overturning
1.91, and
N
is not within the middle third of the base of the wall.
10.9
For the example problem in Sec. 10.2.5, the internal stability of the mechanically
stabilized zone is to be checked by using wedge analysis. Assume a planar slip surface that
is inclined at an angle of 61
(i.e.,
61
) and passes through the toe of the mechani-
cally stabilized zone. Also assume that the mechanically stabilized zone contains 40 hori-
zontal layers of Tensar SS2 geogrid which has an allowable tensile strength
300 lb
ft of
wall length for each geogrid. In the wedge analysis, these 40 layers of geogrid can be repre-
sented as an allowable horizontal resistance force
12,000 lb
ft of wall length (i.e., 40
layers times 300 lb). If the friction angle
of the sand
32
in the mechanically stabilized zone,
calculate the factor of safety for internal stability of the mechanically stabilized zone, using the
wedge analysis for static and earthquake conditions.
Answer:
Static conditions: FS
1.82;
earthquake conditions: FS
1.29.
Sheet Pile Wall Analyses for Liquefied Soil
10.10
For the example problem in Sec. 10.3.3, assume that there is a uniform vertical
surcharge pressure
200 lb
ft
2
applied to the ground surface behind the sheet pile wall.
Calculate the factor of safety for toe kick-out and the anchor pull force for the static condition
and the earthquake conditions, using the pseudostatic method, and for partial liquefaction of
the passive wedge.
Answer:
See App. E for solution.
10.11
For the example problem in Sec. 10.3.3, assume that the ground surface slopes
upward at a 3:1 (horizontal:vertical) slope ratio behind the sheet pile wall. Calculate the factor
of safety for toe kick-out and the anchor pull force for the static condition and the earthquake
conditions, using the pseudostatic method, and for partial liquefaction of the passive wedge.
Answer:
See App. E for solution.
10.12
For the example problem in Sec. 10.3.3, assume that the ground in front of the
sheet pile wall (i.e., the passive earth zone) slopes downward at a 3:1 (horizontal:vertical)
slope ratio. Calculate the factor of safety for toe kick-out for the static condition and the
earthquake conditions, using the pseudostatic method.
Answer:
Static condition: FS for toe
kick-out
1.04.
10.13
For the example problem in Sec. 10.3.3, assume that the anchor block is far enough
back from the face of the sheet pile wall that it is not in the active zone. Also assume that the
anchor block is located at a depth of 3 to 5 ft below ground surface, it is 5 ft by 5 ft in plan
dimensions, and it consists of concrete that has a unit weight of 150 lb
1.18; earthquake condition: FS for toe kick-out
ft
3
. Further assume that
the tieback rod is located at the center of gravity of the anchor block. For friction on the top and
bottom of the anchor block, use a friction coefficient
2
, where
friction angle of the
3
