土木專(zhuān)業(yè)外文翻譯3-建筑結(jié)構(gòu)-預(yù)覽頁(yè)
【正文】 ite, the functions of the dam, and cost factors. Site investigation and testing. Investigation of a site for a dam includes sinking trial borings to determine the strata. The borings are supplemented by shafts and tunnels which, because of their cost, must be used as sparingly as possible. In the shafts and tunnels, tests can be made to measure strength, elasticity, permeability, and prevailing stresses in strata, with particular attention given to the properties of thin partings, or walls, between the more massive beds, The presence in groundwater of chemical solutions harmful to the materials to be used in the construction of the dam must be assessed. Sources of construction materials need exploration. As dams continue to increase in height, the study of foundation conditions bees increasingly critical. Models are particularly useful in analysis of arch dams and in verifying analytical stress calculations. Various materials have been used for model tests。 all were embankment dams of relatively small height. Despite a great deal of work on the distribution of seismic activity, the measurement of strong ground motions, and the response of dams to such motions, earthquake design of dams remains imprecise. The characteristics of strong ground motions at a given site cannot be predicted, and all types of dams possess some degree of freedom, imperfect elasticity, and imprecise damping. Nevertheless, the digital puter and model testing have given promise of considerable progress. It is now possible calculate the response of a concrete dam to any specified ground motion。 大壩的某些輔助功能包括溢洪道、水閘，或利用自身閥門(mén)來(lái)控制從大壩中排出多余的水到下游；吸水結(jié)構(gòu)引水到發(fā)電站或運(yùn)河、隧道，或渠道用于更遠(yuǎn)距離的使用。 大壩從外觀和建筑材料可以分成幾個(gè)不同的級(jí)別，建哪一類(lèi)的大壩的結(jié)論很大程度要根據(jù)山地的基礎(chǔ)條件和方便就地使用的建材。根據(jù)水壓程度利用結(jié)構(gòu)自重或采用橫跨山谷由倆邊峽谷支撐的水平橫拱來(lái)抵抗側(cè)向位移。 地質(zhì)研究和試驗(yàn)，壩址研究包括沉降試驗(yàn)和地層鉆孔測(cè)試。建筑原料需要經(jīng)過(guò)反復(fù)的試驗(yàn)。各類(lèi)建筑材料都將用于模型試驗(yàn)之中，在 Hoover 5 大壩的一些早期試驗(yàn)重，科學(xué)家常利用橡膠來(lái)作為試驗(yàn)材料模型，這需要在復(fù)雜模型中準(zhǔn)確復(fù)制應(yīng)力樣本，模型要符合使用低彈型材料的特性。 大壩設(shè)計(jì)的主要問(wèn)題： 關(guān)于大壩材料基本上有兩種材料：混凝土和泥域填石，但是它們?cè)诖髩蔚恼_設(shè)計(jì)中都有一些弱點(diǎn)需要被克服。 很多快捷的方法被用于解決這方面的問(wèn)題，混凝土常被分層限厚澆筑，裂口被用來(lái)散發(fā)熱量而被最后澆筑。也 就是能滿足強(qiáng)度，其次能抵抗氣候和化學(xué)侵蝕。表面活性劑和加氣劑都被允許用于低水灰比的混凝土，用冰代替水的技巧增加了冷卻速度。土填當(dāng)然是最經(jīng)濟(jì)的，也常適合用于借土合攏壩址。 盡管針對(duì)地震活動(dòng)分布，強(qiáng)地震運(yùn)動(dòng)的量測(cè)水壩對(duì)這種運(yùn)動(dòng)的反應(yīng)做了大量工作，水壩的地震設(shè)計(jì)依然不夠精確，強(qiáng)的地質(zhì)運(yùn)動(dòng)特征給壩址帶來(lái)不
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