Safety of Existing Dams Evaluation and Improvement (1983) / Chapter Skim
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9. Reservoir Problems
9. Reservoir Problems
Pages 272-277
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From page 272... ...
The Vaiont reservoir slide is a spectacular and catastrophic example (see Figure 9-1~. These movements can be initiated by changes in the piezometric conditions within the mass as a result of reservoir loading, saturation of soil and weak rock materials with a resulting lowering of the internal coefficient of friction, erosion and subsequent undercutting of large earth masses by wave action and reservoir operations (raising and lowering)
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From page 273... ...
Increases in the siltation of a reservoir, whether from slide materials or normal sedimentation processes, can reduce the reservoir capacity to store floods. As a result overtopping can occur if such reduced storage capacity has not been considered in the dam and spillway design.
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From page 274... ...
g., the weight of the reservoir may increase stresses at epicentral depths sufficiently to trigger fault activity (there is little to support this thesis) , the downward movement of reservoir water may increase hydrostatic pressures in the rock masses (this increase presumably would increase pressure on a fault plane that may be under a critical state of strain)
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From page 275... ...
ICE The development of an ice layer on a reservoir surface can cause structural damage and produce maintenance difficulties. The main damage is commonly from the impact of ice against thin-walled structures such as parapets on masonry dams.
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From page 276... ...
Ice can also block spillway control structures, particularly gated ones, thereby reducing the spillway capacity, raising the water level, or resulting in a sudden water surge when the ice finally breaks loose. A number of empirical formulas have been proposed for calculating ice loads on a dam.
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From page 277... ...
The latter is important because the rate of temperature rise and its duration can determine the pressure likely to be exerted. Figure 9-2 compares ice pressure with ice thickness and considers whether the reservoir banks act as a restraint.
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