Geologic Hazards - Geotechnical Engineering Investigation - page 715

FIGURE 9.12
Trees bent in the lower portions and
then growing straight up indicate long-
term slope movements. The scarp in the
photo is the head of a progressive
failure in marine shales extending
downslope for over a kilometer near
Bandung, Java.

9.2.3 Planar Slides in Rock Masses

General
Forms of planar slides in rock masses include:

Block glide involving a single unit of relatively small size (photo, Figure 9.15) .

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Slab glide involving a single unit of relatively small to large size (photo, Figure
9.16) .

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Wedge failures along intersecting planes involving single to multiple units, small
to very large in size ( Figure 9.2d) . A small wedge failure is illustrated in Figure
9.81.

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Translational slide: Sliding as a unit, or multiple units, downslope along one
or more planar surfaces (Figure 9.2b). Failure often is progressive ( Section
9.2.6) .

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Massive rock slide involving multiple units, small to very large in size, often
with very high velocities ( Figure 9.17) .

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Block and slab slides can be destructive, but massive rock slides are often disastrous in
mountainous regions and in many cases cannot be prevented, only avoided.