Civil Engineering Reference
In-Depth Information
9.2
Use the data from Prob. 9.1, except assume that the slip surface has an effective
shear strength of
c
3.4 kPa (70 lb/ft
2
) and
29
. Also assume that piezometers have
been installed along the slip surface, and the average measured steady-state pore water
pressure
u
2.4 kPa (50 lb/ft
2
). Calculate the factor of safety of the failure wedge based
on an effective stress analysis for the static case and an earthquake condition of
k
h
0.2.
Assume that the shear strength does not decrease with strain (i.e., not a weakening-type
soil) and the pore water pressures will not increase during the earthquake.
Answer:
Static
FS
1.95, pseudostatic FS
1.15.
9.3
A near-vertical rock slope has a continuous horizontal joint through the toe of the
slope and another continuous vertical joint located 10 ft back from the top of the slope. The
height of the rock slope is 20 ft, and the unit weight of the rock is 140 lb/ft
3
. The shear
strength parameters for the horizontal joint are
c
40
, and the pore water
pressure
u
is equal to zero. For the vertical joint, assume zero shear strength. Neglecting
possible rotation of the rock block and considering only a sliding failure, calculate the pseu-
dostatic factor of safety if
k
h
0.50.
Answer:
Pseudostatic FS
1.68.
0 and
Pseudostatic Analysis Using the Method of Slices
9.4
Use the data from the example problems in Secs. 9.2.7 and 9.3.2. Calculate the
pseudostatic factor of safety if
k
h
0.30.
Answer:
Pseudostatic FS
0.88.
Newmark Method
9.5
Use the data from Prob. 9.1, and calculate the slope deformation based on the
Newmark method [i.e., Eq. (9.3)].
Answer: d
0.06 cm.
9.6
Use the data from Prob. 9.2, and calculate the slope deformation based on the
Newmark method [i.e., Eq. (9.3)].
Answer:
Since pseudostatic FS
1.0,
d
0.
9.7
Use the data from Prob. 9.2 and assume
k
h
0.5. Calculate the slope deformation
based on the Newmark method [i.e., Eq. (9.3)].
Answer: d
2.3 cm.
Weakening Slope Stability Analysis: Flow Slides
9.8
Use the data from Prob. 6.12. Assume the subsoil profile shown in Fig. 6.13 per-
tains to a level-ground site that is adjacent to a riverbank. The riverbank has a 3:1 (hori-
zontal:vertical) slope inclination, and assume that the average level of water in the river
corresponds to the depth of the groundwater table (1.5 m below ground surface). Further
assume that the depth of water in the river is 9 m. Will the riverbank experience a flow fail-
ure during the design earthquake? What type of flow failure is expected?
Answer:
A mass
liquefaction flow failure would develop during the earthquake.
9.9
Use the data from Prob. 6.15. Assume the subsoil profile shown in Fig. 6.15 pert-
ains to a level-ground site that is adjacent to a riverbank. The riverbank has a 4:1 (horizon-
tal:vertical) slope inclination, and assume that the average level of water in the river
corresponds to the depth of the groundwater table (0.4 m below ground surface). Further
assume that the depth of water in the river is 5 m. Will the riverbank experience a flow fail-
ure during the design earthquake? What type of flow failure is expected?
Answer:
A mass
liquefaction flow failure would develop during the earthquake.
9.10
Use the data from Prob. 6.18. Assume the
N
value data shown in Fig. 6.11 per-
tain to a level-ground site that is adjacent to a riverbank. The riverbank has a 3:1
