土木專業(yè)外文翻譯3-建筑結構-文庫吧資料
2025-05-22 14:30本頁面
【正文】 ss water from surfaces by vacuum. Weaknesses of earth and rock fill. Soils and rock fragments lack the strength of concrete, are much more permeable, and possess less resistance to deterioration and disturbance by flowing water. These disadvantages are pensated for by a much lower cost and by the ability of earth fill to adapt to deformation caused by movements in the dam foundation. This assumes, of course, sufficient usable soil available close to the dam site. In bare mountain country it may be necessary to quarry rock and construct a rockfill rather than an rarthfill dam. Earth fill is of course more economical, and often a suitable borrow area can be found close to the site. Soil consists of solid particles with water and air in between. When the soil is pressed by loading, as occurs in dam construction, some drainage of air and water takes place, causing an increase in pressures between the solid particles. When there is a high rate of seepage, the soil tends to develop differential pressures and reach a condition called quick, in which it behaves 3 as a fluid. Even if it does not reach this condition, there is often some weakening of its structure, and steps must be taken to counter this. The earthquake problem. Many large dams have been built in the seismically active regions of the world, including Japan, the western United States, New Zealand, the Himalayas, and the Middle East. In 1968, the Tokachi earthquake damaged 93 dams in Honshu, the main Japanese Island。 on some early tests for Hoover Dam, rubber was employed. The need for accurate reproduction of stress patterns in plex models is met by using material of low elasticity. In a sense, dams themselves are models for future design. The instruments built into them to record movements under load, strains within materials after construction, temperature and pressure changes, and other factors are installed primarily to study the performance of the structure and to warn of possible emergencies, but their value in confirming design assumptions is important. The digital puter has permitted considerable advance in analytical methods of design. Its ability to handle a great volume of dat
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