Environmental Engineering Reference
In-Depth Information
FIGURE 9.23
Stereo-pair of aerial photos showing tension cracks of incipient slides, such as at (1), along the California coast,
a short distance from Portuguese Bend.
Tension crack
Scarps
FIGURE 9.24
During the intermediate stage (during partial failure),
residual soils often fail progressively, forming a series of
slumps in tropical climates. Blocks move downhill during
rainy periods and stabilize during dry periods.
Toe bulge
Serial of shallow
failures
Residual soil
progressive failure tension cracks open and scarps form, separating large blocks. The
cracks can extend far beyond the slope face when a large mass goes into tension, even
affecting surface structures as shown in
Figure 9.30.
Final failure may not develop for
many years, and when it occurs it may be in a form resembling a large slump slide, or it
may develop into a flow with individual blocks floating in a highly disturbed mass,
depending upon natural conditions as described in the examples below.
Failure Examples
Marine Shales: General
Clay shales, particularly those of marine origin, are susceptible to several modes of slope
failures as shown in
Figure 9.31
,
of which progressive failure involves the largest volumes
