土石壩外文翻譯---土石壩及溢洪道設(shè)計-其他專業(yè)(已修改)
2025-02-04 08:34 本頁面
【正文】 The Design of EarthRock Dam and Spillways Part 1 Embankment Dams Selection of embankment type： In general, there are two types of embankment dams: earth and rockfill. The selection is dependent upon the usable materials from the required excavation and available borrow. It should be noted that rockfills can shade into soil fills depending upon the physical character of the rock and that no hard and fast system of classification can be made. Rocks which are soft and will easily break down under the action of excavation and placement can be classified with earthfills. Rocks which are hard and will not break down significantly are treated as rockfills. The selection and the design of earth embankment are based upon the judgment and experience of the designer and is to a large extent of an empirical nature. The various methods of stability and seepage analyses are used mainly to confirm the engineer’s judgment. Freeboard ： All earth dams must have sufficient extra height known as freeboard to prevent overtopping by the pool. The freeboard must be of such height that wave action, wind setup, and earthquake effects will not result in overtopping of the dam. In addition to freeboard, an allowance must be made for settlement of the embankment and the foundation which will occur upon pletion of the embankment. Top width ： The width of the earth dam top is generally controlled by the required width of fill for ease of construction using conventional equipment. In general, the top width should not be less than 30 ft. If a danger exists of an overtopping wave caused either by massive landslides in the pool or by seismic block tipping, then extra top width of erosion resistive fill will be required. Alignment ： construction costs but such alignment should not be such as to encourage sliding or cracking of the embankment. Normally the shortest straight line across the valley will be satisfactory, but local topographic and foundation conditions may dictate otherwise. Dams located in narrow valleys often are given an alignment which is arched upstream so that deflections of the embankment under pool load will put the embankment in pression thus minimizing transverse cracking, Abutments ： Three problems are generally associated with the abutments of earth dams:①seepage,② instability, and ③ transverse cracking of the embankment. If the abutment consists of pervious soils it may be necessary to construct an upstream impervious blanket and downstream drainage measures to minimize and control abutment seepage. Where steep abutments exist, especially with sudden changes of slopes or with steep bluff, there exists a danger of transverse cracking of the embankment fills, This can be treated by excavation of the abutment to reduce the slope, especially in the imperious and transition zones. The transition zones, especially the upstream, should be constructed of fills which have little or no cohesion and a welldistributed gradation of soils which will promote selfhealing should transverse cracking occur. Stage construction ： It is often possible and in
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