土石壩外文翻譯---土石壩及溢洪道設(shè)計-其他專業(yè)-展示頁
2025-01-31 08:34本頁面
【正文】 Some designs will use one type of spillway for normal operation and for flood peaks up to a 50year or 100year frequency storm. An emergency spillway provides additional safety if emergencies arise that was not covered by normal design assumptions. Such situations could result from floods above a certain level, malfunctioning spillway gates, or enforced shutdown of outlet works. The emergency spillway prevents overtopping the main portion of the dam and is particularly needed for earth and rock embankments. The overflow spillway is well suited to concrete dams. It is monly used where dams have sufficient crest length for the desired discharge capacity and where the foundation material is solid or can be protected against scouring. Some dams use a free overflow or nonsupported type。 ⑤ internal movement and strain indicators。 ③ settlement gages。③ a wet borrow area which requires a slow cases it may construction to permit an increase in shear strength through consolidation of the fill. In some cases it may be necessary to provide additional drainage of the foundation or fill by means of sand drain wells or by means of horizontal pervious drainage blankets. Embankment soils ： Most soils are suitable for use for embankment construction, however, there are physical and chemical limitations, soils which contain excessive salts or other soluble materials should not be used. Substantial anic content should not exist in soils. Lignite sufficiently scattered through the fill to prevent the danger of spontaneous bustion, is not objectionable. Fat clays with high liquid limits may prove difficult to work and should be avoided. Compaction requirements ： The strength of the impervious and semiimpervious soils depends upon he pacted densities. These depend in turn upon the water content and weight of the pacting equipment. The design of the embankment is thus influenced by the water content of the fill or after placement practicable alternations to the water content either prior to placement of the fill or after placement but prior to rolling. If the natural water content is too high, then it may be reduced in borrow area by drainage, or by harrowing. If the soil is too dry it should be moistened in the borrow area either by sprinkling or by ponding and then permitted to stabilize the moisture content before use. The range of placement water content is generally between 2 percent dry to 2 or 3 percent wet of the standard Proter optimum water content. Pervious soils should be conpacted to at least 80 percent of relative density. If necessary, test fills should be constructed with variations in placement water content, lift thickness, number of roller passes and type of rollers. For cases of steep abutment, the fill must be placed in thin lifts and pacted by mechanical hand tampers. All overhangs should either be removed or filled with lean concrete prior to fill placement. Types of instruments ： The type of instrumentation depends upon the size and plexity of the project. The devices in mon use are :① piezometers。 The Design of EarthRock Dam and Spillways
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