Civil Engineering Reference
In-Depth Information
FIGURE 9.34
Earthquake damage to a two-lane road in Santa
Cruz Mountains. The slope movement was caused by the Loma
Prieta earthquake in California on October 17, 1989. (
Photograph
from the Loma Prieta Collection, EERC, University of California,
Berkeley.
)
3.
Reduce the hazard to an acceptable level:
Unstable slopes affecting a project can
be rendered stable (i.e., by increasing the factor of safety to greater than 1.5 for static and
greater than 1.1 for dynamic loads) by eliminating the slope, removing the unstable soil
and rock materials, or applying one or more appropriate slope stabilization methods (such
as buttress fills, subdrains, soil nailing, or crib walls). For deep-seated slope instability,
strengthening the design of the structure (e.g., reinforced foundations) is generally not by
itself an adequate mitigation measure.
Mitigation options for various types of earthquake-induced slope movement are as follows:
A.
Mitigation options for potential rockfalls and rock slides (see Table 9.1)
1.
Reduce the driving forces:
This can be accomplished by flattening the slope
inclination, removing the unstable or potentially unstable rocks, diverting water
from the slope face, and incorporating benches into the slope (Piteau and
Peckover 1978).
