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gravity dam[′grav·əd·ē ‚dam]
a dam of reinforced concrete or stone whose resistance to forces trying to move it (the pressure of water, ice, waves, and so on) is provided principally by the forces of friction along the foundation proportional to the weight of the dam itself.
The use of a gravity dam is widespread in both rocky locations (such as in the Bukhtarma and Krasnoiarsk hydroelectric power plants) and in nonrocky soils (such as in overflow dams of the Volga hydroengineering complexes). The most economical form of its cross section is similar to a triangle or a trapezoid. The principal parameter of a gravity dam is the ratio of the thickness of the dam at its base to its height, which depends on the characteristics of the supporting soil or of the rock. This parameter varies from 0.6 for rock to 1.2 for clay. The tallest existing gravity dam (1970) is 284 m (the Grande Dixence Dam in Switzerland).
The existence of a considerable strength factor in a gravity dam permits simplification in construction by use of wide temperature, keyed expansion joints (Bratsk Hydroelectric Power Plant), cavities filled with ballast or lacking ballast (Votkinsk Hydroelectric Power Plant), longitudinal galleries, and other engineering approaches that facilitate the work of the dam and reduce its cost.
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