Environmental Engineering Reference
In-Depth Information
9
Landslides and Other Slope Failures
9.1
Introduction
9.1.1
General
Origins and Consequences of Slope Failures
Gravitational forces are always acting on a mass of soil or rock beneath a slope. As long as the
strength of the mass is equal to or greater than the gravitational forces, the forces are in bal-
ance, the mass is in equilibrium, and movement does not occur. An imbalance of forces results
in slope failure and movement in the forms of creep, falls, slides, avalanches, or flows.
Slope failures can range from being a temporary nuisance by partially closing a road-
way, to destroying structures, to being catastrophic and even burying cities.
Failure Oddities
Prediction:
Some failures can be predicted, others cannot, although most haz-
ardous conditions are recognizable.
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Occurrence
: Some forms occur without warning; many other forms give warning,
most commonly in the form of early surface cracks.
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Movement velocities
: Some move slowly, others progressively or retrogressively,
others at great velocities.
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Movement distances
: Some move short distances; others can move for many miles.
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Movement volume
: Some involve small blocks; others involve tremendous volumes.
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Failure forms
: Some geologic formations have characteristic failure forms; others
can fail in a variety of forms, often complex.
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Mathematical analysis
: Some conditions can be analyzed mathematically, many
cannot.
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Treatments
: Some conditions cannot be treated to make them stable; they should
be avoided.
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Objectives
The objectives of this chapter are to provide the basis for:
Prediction of slope failures through the recognition of the geologic and other
factors that govern failure
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Treatment of slopes that are potentially unstable and pose a danger to some
existing development
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Design and construction of stable cut slopes and sidehill fills
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Stabilization of failed slopes
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