Environmental Engineering Reference
In-Depth Information
FIGURE 10.37
Debris in Johnstown, PA, following the dam's failure. (From Wikimedia Commons.)
Figures 10.38 and 10.39 illustrate, respectively, the 1995 gate failure of Folsom Dam and the
2010 Delhi Dam failure in Iowa, neither of which resulted in loss of life.
Major causes of dam failure include (NRC 1983):
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Overtopping—34% of all failures (nationally)
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Inadequate spillway design
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Debris blockage of spillway
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Settlement of dam crest
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Foundation defects—30% of all failures
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Differential settlement
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Sliding and slope instability
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High uplift pressures
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Uncontrolled foundation seepage
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Piping and seepage—20%
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Internal erosion through dam caused by seepage—“piping”
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Seepage and erosion along hydraulic structures such as outlets
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Conduits or spillways, or leakage through animal burrows
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Cracks in the dam
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Conduits and valves—10%
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Piping of embankment material into conduit through joints or cracks
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Other—6%
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