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2024-12-13 22:12本頁(yè)面
【正文】 enance of dams are monly under government surveillance. In the United States over 30,000 dams are under the control of state authorities. The 1972 Federal Dams Safety Act (PL92367)requires periodic inspections of dams by qualified experts. The failure of the Teton Dam in Idaho in June 1976 added to the concern for dam safety in the United States. 1 Type of Dams Dams are classified on the type and materials of construction, as gravity, arch, buttress ,and earth .The first three types are usually constructed of concrete. A gravity dam depends on its own weight for stability and it usually straight in plan although sometimes slightly curved. Arch dams transmit most of the horizontal thrust of the water behind them to the abutments by arch action and have thinner cross sections than parable gravity dams. Arch dams can be used only in narrow canyons where the walls are capable of withstanding the thrust produced by the arch action. The simplest of the many types of buttress dams is the slab type, which consists of sloping flat slabs supported at intervals by buttresses. Earth dams are embankments of rock or earth with provision for controlling seepage by means of dam may be included in a single structure. Curved dams may bine both gravity and arch action to achieve stability. Long dams often have a concrete river section containing spillway and sluice gates and earth or rockfill wing dams
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