Civil Engineering Reference
In-Depth Information
FIGURE 9.37
Earthquake-induced landslide movement that damaged the south abutment of the Shih-Wui
Bridge. The landslide was caused by the Chi-chi (Taiwan) earthquake on September 21, 1999. (
Photograph
from the Taiwan Collection, EERC, University of California, Berkeley.
)
2.
Increase the stability:
Retaining the individual blocks of rock on the slope face
can increase the slope stability. Measures to increase the stability of the slope
include the installation of anchoring systems (such as bolts, rods, or dowels), apply-
ing shotcrete to the rock slope face, and constructing retaining walls.
3.
Protect the site:
For rockfalls, it may be possible to intercept or deflect the falling
rocks around the structure. This can be accomplished by using toe-of-slope ditches,
wire mesh catch fences, and catch walls (Peckover 1975). Recommendations for the
width and depth of toe-of-slope ditches are given by Ritchie (1963) and Piteau and
Peckover (1978).
B.
Mitigation options for potential soil slides (see Table 9.2)
1.
Reduce the driving forces:
This can be accomplished by reducing the weight of
the potential slide mass by cutting off the head of the slide or totally removing the
slide. Other options include flattening the slope inclination through grading,
preventing water infiltration by controlling surface drainage, and lowering the
groundwater table by installing subsurface drainage systems in order to dewater
the slide mass.
2.
Increase the stability:
A shear key or buttress can be constructed to increase the
stability of the slope. Other options include the construction of pier walls or retain-
ing walls, and the pinning of shallow slide masses with soil anchors or nails.
C.
Mitigation options for potential flow slides and lateral spreading (see Table 9.2)
1.
Reduce the driving forces:
This can be accomplished by removing the liquefac-
tion-prone material from the site, using grading or excavation techniques. Other
options include lowering the groundwater table by using subsurface galleries or
subdrains so that the soil is no longer susceptible to liquefaction.
