混凝土大壩外文翻譯--混凝土重力壩的設(shè)計(jì)分析與比較-文庫吧
2025-04-16 21:44 本頁面
【正文】 avity dams, constructed in stone masonry, were built even in ancient times, most often in Egypt, Greece, and the Roman Empire [2,3]. However, concrete gravity dams are preferred these days and mostly constructed. They can be constructed with ease on any dam site, where there exists a natural foundation strong enough to bear the enormous weight of the dam. Such a dam is generally straight in plan, although sometimes, it may be slightly curve. The line of the upstream face of the dam or the line of the crown of the dam if the upstream face in sloping, is taken as the reference line for layout purposes, etc. and is known as the “Base line of the Dam” or the “Axis of the Dam”. When suitable conditions are available, such dams can be constructed up to great heights. The ratio of base width to height of high gravity dams is generally less than 1:1. A typical crosssection of a high concrete gravity dam is shown in Figure . The upstream face may be kept throughout vertical or partly slanting for some of its length. A drainage gallery is generally provided in order to relieve the uplift pressure exerted by the seeping applicable to dam construction may include navigation, flood damage reduction, hydroelectric power generation, fish and wildlife enhancement, water quality, water supply, and recreation. Many concrete gravity dams have been in service for over 50 years, and over this period important advances in the methodologies for evaluation of natural phenomena hazards have caused the designbasis events for these dams to be revised upwards. Older existing dams may fail to meet revised safety criteria and structural rehabilitation to meet such criteria may be costly and difficult. The identified causes of failure, based on a study of over 1600 dams [4] are: Foundation problems (40%), Inadequate spillway (23%), Poor construction (12%), Uneven settlement (10%), High poor pressure (5%), Acts of war (3%), Embankment slips (2%), Defective ma terials(2%), Incorrect operation (2%), and Earthquakes (1%).Other surveys of dam failure have been cited by [5], who estimated failure rates from 2104to7 104per damyear based on these surveys. In the design of gravity concrete, it is essential to determine the loads required in the stability and stress analyses. The forces which may affect the design are: 1) Dead load or stabilizing force。 2) Headwater and tailwater pressures。 3) Uplift。 4) Temperature。 5) Earth and silt pressures。 6) Ice pressure。 7) Earth quake forces。 8) Wind pressure。 9) Subatmospheric pressure。 10) Wave pressure, and 11) Reaction of foundation. The seismic safety of such dams has been a serious concern since damage to the Koyna Dam in India in 1967 which has been regarded as a watershed event in the development of seismic analysis and design of concrete gravity dams all over the world. It is essential that those responsible must implement policies and proce dures to ensure seismic safety of dams through sound professional practices and stateoftheart in related technical areas. Seismic safety of dams concerns public safety and therefore demands a highe
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