ATOC 185 Lecture 8: ATOC 185 Lectures - Week 8

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October


26th
Landslides


and


Avalanches
Landslides


– part of mass-wasting, rock and debris slides are types of landslides, mass-wasting family
-One of most catastrophic disaster
- Hit without warning
- Storms, earthquakes, volcanic activity, coastal wave attack, fires can produce slope instability
Aberfan


Disaster
- Coal mining village in England (south Wales)
- Coal waste on the hill top
- Rains for 3 weeks
-21 October 1966 – huge landslide, hit many houses
- Deaths: 144 (28 adults, 116 children)
Mass


Wasting
- Moves weathered product from top of hill down
-Occurs when force of gravity exceeds strength of slope material
-Occurrence can be predicted by slope-weakening events
- Earthquakes
-Floods
- Volcanic activity
- Storms or torrential rain
-Synonymous for slope failure
- Failure and downslope movement of rock or unconsolidated materials in response to
gravity
-Developed nations – impacts can result in millions of dollars of damage with some deaths
-Less developed – can be more extensive because of population density, lack of zoning laws,
information or preparedness
-We can’t always predict or prevent occurrence of these events
Factors


that


influence
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
slope
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
stability
1. Gravity and gradient of slope
a. Stay Force: internal resistance to movement
b. Go Force: force causing movement parallel to slope (increases with slope angle)
i. Dependent on angle
c. On a slope, gravity has two components
i. One at right angles to slope (Gp, stay force)
ii. Parallel to slope (Gs, go force)
d. As slope angle increases, Gp (stay) decreases while Gs (go) increases
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Document Summary

Landslides part of mass-wasting, rock and debris slides are types of landslides, mass-wasting family. Storms, earthquakes, volcanic activity, coastal wave attack, fires can produce slope instability. 21 october 1966 huge landslide, hit many houses. Moves weathered product from top of hill down. Occurs when force of gravity exceeds strength of slope material. Occurrence can be predicted by slope-weakening events. Failure and downslope movement of rock or unconsolidated materials in response to gravity. Developed nations impacts can result in millions of dollars of damage with some deaths. We can"t always predict or prevent occurrence of these events. Factors that influence slope stability: gravity and gradient of slope i, stay force : internal resistance to movement, go force : force causing movement parallel to slope (increases with slope angle, on a slope, gravity has two components. If we have hillside less than angle of repose, material is not moving.

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