土木專業(yè)外文翻譯3-建筑結(jié)構(gòu)(存儲(chǔ)版)
【正文】 國(guó)家中大壩更具特殊重要性，在一個(gè)小國(guó)家可以從一個(gè)簡(jiǎn) 單的大壩中獲得巨大的農(nóng)業(yè)和工業(yè)利益。 these are specially blended so that rates of heat evolution are retarded. Cement content can be safely reduced in the interior concrete in the dam, in which strength and resistance to climatic and chemical deterioration are less important. The cement content, and therefore the heat caused by hydrating, can also be reduced by using aggregate (the other major constituent of concrete) of larger stones. Another expedient is to use other finegrained materials, such as fly ash (pulverized fuel), as filler, reducing the total cement volume in the concrete. Another is to use certain additives, surfaceactive agents, and airentraining agents that permit using a lower watertocement ratio in mix by ice, circulating water through pipes laid in the concrete, and extracting excess 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 Stat
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