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(編輯修改稿)
2025-06-25 21:44 本頁面
【文章內(nèi)容簡介】 r degree of public confidence. The Estimations and descriptions of various forces are provided briefly in the following sections. . Water Pressure Water pressure (P) is the most major external force acting on gravity dams. The horizontal water pressure exerted by the weight of water stored on the upstream and downstream sides of the dam can be estimated from the rule of hydrostatic pr essure distribution and can be expressed by where, H is the depth of water and w? is the unit weight of water. . Uplift Pressure Water seepage through the pores, cracks and fissures of the foundation materials, and water seepage through dam body and then to the bottom through the joints between the body of the dam and its foundation at the base exert an uplift pressure on the base of the dam. According to the [6], the uplift pressure intensities at the heel and toe of the dam should be taken equal to their respective hydrostatic pressures and joined the intensity ordinates by a straight line. When 221 Hp w??drainage galleries are provided to relieve the uplift, the remended uplift at the face of the gallery is equal to the hydrostatic pressure at toe plus 1/3rd of the difference between the hydrostatic pressures at the heel and the toe, respectively. . Earthquake Forces An earthquake produces waves, which are capable of shaking the earth upon which the gravity dams rest, in every possible direction. The effect of an earthquake is, therefore, equivalent to imparting acceleration to the foundations of the dams in the direction in which the wave is traveling at the moment. Generally, an earthquake induces horizontal acceleration (h) and vertical acc eleration (v). The values of these accelerations are generally expressed as per centage of the acceleration due to generally sufficient for high dams in seismic zones. In extremely seismic regions and in conservative Designs even a value up to g may sometimes be adopted [7]. Earthquake loadings should be checked for horizontal as well as vertical earth quake accelerations. While earthquake acceleration might take place in any direc tion,the analysis should be performed for the most unfavorable direction. The earthquake loadings used in the design of concrete gravity dams are based on design earthquakes and sitespecific motions determined from seismological eva luation. At a minimum, a seismological evaluation should be performed on all pro jects located in seismic zones 1, 2, and 3 of Bangladesh [8], depending upon the severity of earthquakes. The seismic coefficient method of analysis should be used in determining the resultant location and sliding stability of dams. In strong seismicity areas, a dynamic seismic analysis is required for the internal stress analysis. . Effect of Vertical Acceleration (ɑv) A vertical acceleration may either act downward or upward. When it acts in the upward direction, then the foundation of the dam will be lifted upward and bees closer to the body of the dam, and thus the effective weight of the dam will increase and hence, the stress developed will increase. When the vertical acceleration acts downward, the foundation s
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