水利电力专业外文翻译--溢洪道-桥梁设计(编辑修改稿)

水利电力专业外文翻译--溢洪道-桥梁设计(编辑修改稿)内容摘要：

ar strength In practice, shearing of concrete is always acpany pression and tension caused by bending, and even in testing is impossible to staminate an element of bending. RESERVOIRS When a barrier is constructed across some river in the form of a dam, water gets stored up on the upstream side of the barrier, forming a pool of water, generally called a reservoir. 5 Broadly speaking, any water collected in a pool or a lake may be termed as a reservoir. The water stored in reservoir may be used for various purposes. Depending upon the purposes served, the reservoirs may be classified as follows: Storage or Conservation Reservoirs. Flood Control Reservoirs. Distribution Reservoirs. Multipurpose reservoirs. (1) Storage or Conservation Reservoirs. A city water supply, irrigation water supply or a hydroelectric project drawing water directly from a river or a stream may fail to satisfy the consumers’ demands during extremely low flows, while during high flows。 it may bee difficult to carry out their operation due to devastating floods. A storage or a conservation reservoir can retain such excess supplies during periods of peak flows and can release them gradually during low flows as and when the need arise. Incidentally, in addition to conserving water for later use, the storage of flood water may also reduce flood damage below the reservoir. Hence, a reservoir can be used for controlling floods either solely or in addition to other purposes. In the former case, it is known as ‘Flood Control Reservoir’ or ‘Single Purpose Flood Control Reservoir’, and in the later case, it is called a ‘Multipurpose Reservoir’. (2) Flood Control Reservoirs A flood control reservoir or generally called floodmitigation reservoir, stores a portion of the flood flows in such a way as to minimize the flood peaks at the areas to be protected downstream. To acplish this, the entire inflow entering the reservoir is discharge till the outflow reaches the safe capacity of the channel downstream. The inflow in excess of this rate is stored in stored in the reservoir, which is then gradually released so as to recover the storage capacity for next flood. The flood peaks at the points just downstream of the reservoir are thus reduced by an amount AB. A flood control reservoir differs from a conservation reservoir only in its need for a large sluiceway capacity to permit rapid drawdown before or after a flood. Types of flood control reservoirs. There are tow basic types of floodmitigation reservoir. Storage Reservoir or Detention basins. Retarding basins or retarding reservoirs. A reservoir with gates and valves installation at the spillway and at the sluice outlets is known as a storagereservoir, while on the other hand, a reservoir with ungated outlet is known as a retarding basin. Functioning and advantages of a retarding basin: A retarding basin is usually provided with an uncontrolled spillway and an uncontrolled orifice type sluiceway. The automatic regulation of outflow depending upon the availability of water takes place from such a reservoir. The maximum discharging capacity of such a reservoir should be equal to the maximum safe carrying capacity of the channel downstream. As flood occurs, the reservoir gets filled and discharges through sluiceways. As the reservoir elevation increases, outflow discharge increases. The water level goes on rising until the flood has subsided and the inflow bees equal to or less than the outflow. After this, water gets automatically withdrawn from the reservoir until the stored water is pletely discharged. The advantages of a retarding basin over a gate controlled detention basin are: ① Cost of gate installations is save. 6 ② There are no fates and hence, the possibility of human error and negligence in their operation is eliminated. Since such a reservoir is not always filled, much of land below the maximum reservoir level will be submerged only temporarily and occasionally and can be successfully used for agriculture, although no permanent habitation can be allowed on this land. Functioning and advantages of a storage reservoir: A storage reservoir with gated spillway and gated sluiceway, provides more flexibility of operation, and thus gives us better control and increased usefulness of the reservoir. Storage reservoirs are, therefore, preferred on large rivers which require batter controlled and regulated properly so as not to cause their coincidence. This is the biggest advantage of such a reservoir and outweighs its disadvantages of being costly and involving risk of human error in installation and operation of gates. (3) Distribution Reservoirs A distribution reservoir is a small storage reservoir constructed within a city water supply system. Such a reservoir can be filled by pumping water at a certain rate and can be used to supply water even at rates higher than the inflow rate during periods of maximum demands (called critical periods of demand). Such reservoirs are, therefore, helpful in permitting the pumps or water treatment plants to work at a uniform rate, and they store water during the hours of no demand or less demand and supply water from their ‘storage’ during the critical periods of maximum demand. (4) Multipurpose Reservoirs A reservoir planned and constructed to serve not only one purpose but various purposes together is called a multipurpose reservoir. Reservoir, designed for one purpose, incidentally serving other purpose, shall not be called a multipurpose reservoir, but will be called so, only if designed to serve those purposes also in addition to its main purpose. Hence, a reservoir designed to protect the downstream areas from fl。