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Gravitational failure of sea cliffs in weakly lithified sediment

Environmental and Engineering Geoscience

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DOI: 10.2113/8.3.175

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Abstract

Gravitational failure of sea cliffs eroded into weakly lithified sediment at several sites in California involves episodic stress-release fracturing and cantilevered block falls. The principal variables that influence the gravitational stability are tensional stresses generated during the release of horizontal confining stress and weakening of the sediment with increased saturation levels. Individual failures typically comprise less than a cubic meter of sediment, but large areas of a cliff face can be affected by sustained instability over a period of several days. Typically, only the outer meter or so of sediment is removed during a failure episode. In-place sediment saturation levels vary over time and space, generally being higher during the rainy season but moderate to high year-round. Laboratory direct-shear tests show that sediment cohesion decreases abruptly with increasing saturation level; the decrease is similar for all tested sediment if the cohesion is normalized by the maximum, dry-sediment cohesion. Large failures that extend over most or all of the height of the sea cliff are uncommon, but a few large wedge-shaped failures sometimes occur, as does separation of large blocks at sea cliff-gully intersections.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Gravitational failure of sea cliffs in weakly lithified sediment
Series title:
Environmental and Engineering Geoscience
DOI:
10.2113/8.3.175
Volume
8
Issue:
3
Year Published:
2002
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
175
Last page:
191
Number of Pages:
17