水利水电英语课文翻译
水利水电英语课文翻译水利水电英语课文翻译课文翻译需要掌握一定的词汇和技巧，当然英语课文翻译可以帮助提高学生的英语水平。
以下是店铺整理的水利水电英语课文翻译，欢迎阅读。
水利水电英语课文翻译1：Lesson 1 importance of water 水的重要性Water is best known and most abundant of all chemical compounds occurring in relatively pure form on the earth‘s surface. Oxygen, the most abundant chemical element, is present in combination with hydrogen to the extent of 89 percent in water. Water covers about three fourths of the earth's surface and permeates cracks of much solid land. The Polar Regions are overlaid with vast quantities of ice, and the atmosphere of the earth carries water vapor in quantities from 0.1 percent to 2 percent by weight. It has been estimated that the amount of water in the atmosphere above a square mile of land on a mild summer day is of the order of 50,000 tons.在地球表面以相对纯的形式存在的一切化合物中，水是人们最熟悉的、最丰富的一种化合物。
在水中，氧这种最丰富的化学元素与氢结合，其含量多达89%。
水覆盖了地球表面的大约3/4的面积，并充满了陆地上的许多裂缝。
地球的两极被大量的冰所覆盖，同时大气也挟带有占其重量0.1%～2%的水蒸气。
据估计，在温暖的夏日，每平方英里陆地上空大气中的水量约为5万吨。
All life on earth depends upon water, the principal ingredient of living cells. The use of water by man, plants, and animals is universal. Without it there can be no life. Every living thing requires water. Man can go nearly two months without food, but can live only three or four days without water.地球上所有的生命都有赖于水而存在，水是活细胞的基本组分（要素）。
人类、和动物都得用水。
没有水就没有生命。
每一种生物都需要水。
人可以接近两个月不吃食物而仍能活着，但不喝水则只能活三四天。
In our homes, whether in the city or in the country, water is essential for cleanliness and health. The average American family uses from 65,000 to 75,000 gallons of water per year for various household purposes.在我们的家庭中，无论是在城市还是农村，水对于卫生和健康来说都是必不可少的。
美国家庭的年平均用水量达6.5～7.5万加仑。
Water can be considered as the principal raw material and the lowest cost raw material from which most of our farm produces is made. It is essential for the growth of crops and animals and is a very important factor in the production of milk and eggs. Animals and poultry, if constantly supplied with running water, will produce more meat, more milk, and more eggs per pound of food and per hour of labor.水可以被认为是最基本的和最廉价的原料。
我们的农产品，大部分都是由它构成的。
水是农作物和动物生长的要素，也是奶类和蛋类生产的一个很重要的因素。
动物和家禽，如果用流动的水来喂养，那么每磅饲料和每个劳动小时会生产出更多的肉、奶和蛋。
:For example, apples are 87% water. The trees on which they grow must have watered many times the weight of the fruit. Potatoes are 75% water. To grow an acre of potatoes tons of water is required. Fish are 80% water. They not only consume water but also must have large volumes of water in which to live. Milk is 88% water. To produce one quart of milk a cow requires from 3.5 to 5.5 quarts of water. Beef is 77% water. To produce a pound of beef an animal must drink many times that much water. If thereis a shortage of water, there will be a decline in farm production, just as a shortage of steel will cause a decrease in the production of automobiles.例如，苹果含87%的水分，苹果树就必须吸收比苹果多许多倍的水分；土豆含75%的水分，那么种植每英亩土豆就需要若干吨水；牛奶含水量为88%，为了生产每夸脱牛奶，母牛需要3.5～5.5 夸脱的水；牛肉含77%的水，为生产1磅牛肉牛必须饮用许多磅水。
如果缺水，就会使农产品减产，就像缺乏钢会引起汽车产量下降一样。
In addition to the direct use of water in our homes and on the farm, there are many indirect ways in which water affects our lives. In manufacturing, generation of electric power, transportation, recreation, and in many other ways, water plays a very important role.水除了直接为我们的家庭和农场利用外，它还以许多间接的方式对我们的产生影响。
在制造、发电、运输、娱乐以及许多行业，水都起着很重要的作用。
Our use of water is increasing rapidly with our growing population. Already there are acute shortages of both surface and underground waters in many locations. Careless pollution and contamination of our streams, lakes, and underground sources has greatly impaired the quality of the water which we do have available. It is therefore of utmost importance for our future that good conservation and sanitary measures be practiced by everyone.我们对水的利用随人口的增长而迅速增加。
在许多地方，无论地面水或地下水都已经严重短缺了。
由于任意污染河流、湖泊和地下水源，已经大大地损害了人们能够利用的水的水质。
因此，人人有责对水采取保护措施和卫生措施，这对于我们人类的未来是极端重要的。
水利水电英语课文翻译2：Lesson 2 the Hydrologic Cycle 水循环In nature, water is constantly changing from one state toanother. The heat of the sun evaporates water from land and water surfaces, this water vapor (a gas), being lighter than air, rises until it reaches the cold upper air where it condenses into clouds. Clouds drift around according to the direction of the wind until they strike a colder atmosphere. At this point the water further condenses and falls to the earth as rain, sleet, or snow, thus completing the hydrologic cycle.在自然界中，水总是不断地从一种状态改变成另一种状态。
太阳热使陆地和水面上的水蒸气。
水利水电工程专业英语教材翻译
P71 2-1混凝土重力坝类型基本上，重力水坝保持其对设计载荷从几何形状和混凝土的质量和强度稳定坚固的混凝土结构。
一般情况下，它们在一条直线轴构成，但也可以稍微弯曲或成角度，以适应特定的现场条件。
重力坝通常由非溢流坝段（S）和溢出部分或溢洪道。
这两个一般混凝土的施工方法，混凝土重力坝是常规放置大体积混凝土和碾压。
Conventional concrete dams.传统的混凝土大坝。
（1）传统上放置大体积混凝土坝的特点是建筑施工中用的材料和配料使用的技术，混匀，放置，固化和大体积混凝土的温度控制（美国混凝土学会（ACI）207.1 R-87）。
典型溢出和非溢出部分示于图2-1和图2-2。
建筑采用已开发和完善了多年设计和建造大体积混凝土大坝的方法。
普通混凝土的水泥水化过程限制大小和混凝土浇筑的速度和建设就必须在巨石满足裂缝控制要求。
通常采用大尺寸的粗集料，混合比例被选择为产生低坍落度混凝土，使经济，在放置期间保持良好的加工性，水化过程中发育的最低温度上升，并产生重要性能如强度，抗渗性和耐久性。
大坝建设与传统的混凝土容易便于安装管道，压力管道，画廊等，在结构内。
（2）施工过程包括配料和混合，运输，安置，振动，冷却，固化，并准备电梯间的水平施工缝。
在重力坝大体积混凝土通常证明一个现场搅拌站，并需要足够的质量和数量，位于或项目的经济范围内的总根源。
一般是在水桶由卡车，铁路，起重机，索道，或这些方法的组合进行4至12立方码大小不等，从批次厂坝运输。
最大桶大小通常是通过有效地扩散和振动混凝土桩后它被从桶倾倒的能力受到限制。
混凝土被放置在5-升降机至10英尺的深度。
每部电梯由连续层不超过18至20英寸。
振动一般由大的人，气动，开钻式振动器进行。
保洁水平施工缝固化过程中去除表面上的薄弱浮浆薄膜的方法包括绿色切削，湿喷砂和高压气水射流。
传统的混凝土安置的其他详情载于EM 1110-2-2000。
（3）由于水泥水化产生的热量，需要在大体积混凝土的放置和放置几天后仔细的温度控制。
水利水电工程专业英语——河流工程篇
水利水电工程专业英语——河流工程篇1。
Some Problems Related to Alluvial Rivers(1)1。
与冲积河流相关的一些问题(1）Many of the earlier civilizations came into being the fertile valleys of large rivers. Civilizations prospered in the Nile valley in Egypt, along the Tigris and Eupharates rivers in Mesopotamia，along the Indus River. As early as 4000 B。
C. people built dams across the rivers to store water，dug canals for navigation purposes and also to carry water to the fields to produce much-needed food. Together with the problems associated with the irrigation works，these earlier civilizations were confronted with the problems of flood control and the Chinese had developed excellent systems of dikes for the protection of inhabited areas against floods。
很多早期的文明都孕育在大江大河的肥沃的河谷。
这些文明繁荣在在埃及尼罗河谷,沿着美索不达米亚的底格里斯河和幼发拉底河，沿着印度河流域。
早在公元前4000年，人们就横跨河流修建水坝来蓄水，以航运及将水带到农田以生产更加非常需要的事物为目的而开挖渠道.与同灌溉工程相关的问题一样，这些早期文明也面临着防洪的问题，而中国人则已经发展了防洪保护居住区的优秀堤防体系.Thus，since the dawn of civilization, mankind has faced problems associated with rivers，and solved them to the best of their ability。
水利水电工程专业英语Chapter 2 (25-38)
倍数的比较
• A is N times as large (long，heavy……）as B • A is N times larger (longer, heavier…) than B • A is larger (longer、heavier···) than B by N times
The oxygen atom is 16 times heavier than the hydrogen atom。 氧原子的重量是氢原子的16倍。 This substance reacts three times as fast as the other one 这一物质的反应速度比另一物质快两倍。
倍数的减少
half as much as twice less than
• “比……少一半”或“比……少二分之一”
The new engine may use half as much oil as the old one。 新引擎的油耗比旧引擎少一半。 The power output of the machine is twice less than its input。 该机器的输出功率比输入功率小二分之一。
倍数的译法
as+形容词+as+数词+…… 动词+as+副词+数词+…… as large as+数词……可译成“大到(至)……" as many as十数词… 可译成“多达……” as high as+数词…… 可译成“高达……” as low as十数词…… 可译成“低到(至)……” The temperature of liquid nitrogen is as low as -196℃
水利专业英语翻译部分
Lesson1 importa nce of water 水的重要性Water is best known and most abundan t of all chemica l compoun ds occurri ng in relativ ely pureformontheearth’ssurface. Oxygen,the most abundan t chemica l element, is present in combina tion with hydroge n to the extentof 89 percent in water. Water coversabout three fourths of the earth's surface and permeat es cracksof much solid land. The polar regions are overl ai d with vast quantiti es of ice, and the atmosphere of the earth carries water vapor in quantiti es from 0.1 percent to 2 percent by weight.It has been estimat ed that the amountof water in the atmosph ere above a squaremile of land on a mild summerday is of the order of 50,000 tons.在地球表面以相对纯的形式存在的一切化合物中，水是人们最熟悉的、最丰富的一种化合物。
在水中，氧这种最丰富的化学元素与氢结合，其含量多达89%。
水利水电工程专业英语——水文与水资源篇
水利水电工程专业英语——水文与水资源篇1. Hydrological Cycle and Budget1.水文循环与预算Hydrology is an earth science. It encompasses the occurrence, distribution, movement, and properties of the waters of the earth and their environmental relations. Closely allied fields include geology, climatology, meteorology and oceanography.水文学是一门地球科学。
它包含地球水资源的发生、分布、运动和特质，以及其环境关系。
与之密切相关领域包括地质学，气候学，气象学和海洋学。
The hydrologic cycle is a continuous process by which water is transported from the oceans to the atmosphere to the land and back to the sea. Many sub-cycles exist. The evaporation of inland water and its subsequent precipitation over land before returning to the ocean is one example. The driving force for the global water transport system is provided by the sun, which furnishes the energy required for evaporation. Note that the water quality also changes during passage through the cycle; for example, sea water is converted to fresh water through evaporation.水文循环是一个连续的过程，在这个过程中水从海洋被运输到大气中，降落到陆地，然后回到海洋。
水利水电工程专业英语的阅读与翻译
-graph
表示写 ，画， 记录结 果
和用具
photograph 照片，monograph 专题，论文
-let
表示小
droplet 水滴，streamlet 小溪
-logy
表示 学科
hydrology 水文学，geology 地质学
-meter
表示计，仪 表
barometer 气压计，voltmeter 电压表
uni
单，
uniflow 单向流，unify 统一
vari
变化
variable 变量，可变的，variation 变化，偏差
vers
转，向
reverse 反向，transverse 横向
vis
看
visual 直观的，prevision 预见
（2）英 语单词 的词尾 是接在 词根后 面的部 分，一 般地， 词尾的 意义比 较狭窄 和明 确，常 可根据 词尾来 判断英 语中大
水 利水 电工程 专业 英语的 阅读与 翻译
水利水电 工程
专业英语的阅读与翻译 刘景植 编
二 OO 四年十二月
水利水电 工程专 业英语 的阅读 与翻译
前言
当前，世 界科学 技术发 展十分 迅速， 为了了 解、学 习和借 鉴国 外先进 的科学 技术， 为我国 的社会 主义建 设服务 ，需要
大量的阅 读和翻 译国外 科技文 献资料 。另外 ，近年 来和在 以后 的若干 年内， 我国在 水利水 电建设 中，从 国外引 进了且
多数词的 词类。
专业英语 词汇中 的一些 常用的 词尾：
词尾
意义
词例
Ⅰ、名词 词尾
-age
表示抽象概 念，量 ，性质 ，状态 ，行为 等
水利水电工程专业英语段翻译
•Owingto the fact that electr icity can be transm itted from whereit is genera ted to whereit is needed by meansof powerlinesand transf ormer s, largepowerstatio ns can be builtin remote places far fromindust rialcenter s or largecities, as is citedthe case with hydroe lectr ic powerstatio ns that are insepa rable from watersource s.•由于电力可以从发电的地方通过电线和变压器输送到需要用电的地方，因此大型电站可以建在远离工业中心或大城市的地方，离不开水源的水力发电站就常常是这样建立的。
Ideall y suited to narrow canyon s compos ed of rock, the archdam provid es an econom icaland effici ent struct ure to contro lthe stream flow. The load-carryi ng capaci ty of an arch damenable s the design er to conser ve materi al and stillmainta in anextrem ely safe struct ure.•拱坝最适合于修建在岩石峡谷中，它是一种控制河道中水流经济而有效的建筑物。
一座拱坝的承载能力足以使设计人员用较少的材料而仍能建成极为安全的结构。
水利水电专业毕业设计外文翻译
毕业设计（论文）外文翻译题目水库及电力系统简介专业水利水电工程班级2007级四班学生陈剑锋指导教师杨忠超重庆交通大学2011 年RESERVOIRSWhen 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.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 become 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 flood-mitigation 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 accomplish 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 sluice-way capacity to permit rapid drawdown before or after a flood.Types of flood control reservoirs. There are tow basic types of flood-mitigation 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 storage-reservoir, 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 anuncontrolled 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 becomes equal to or less than the outflow. After this, water gets automatically withdrawn from the reservoir until the stored water is completely discharged. The advantages of a retarding basin over a gate controlled detention basin are:①Cost of gate installations is save.②There 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 floods and also to conserve water for water supply, irrigation, industrial needs, hydroelectric purposes, etc. shall be called a multipurpose reservoir.水库拦河筑一条像坝的障碍时，水就被拦蓄在障碍物的上游并形成水塘．通常称之为水库。
水利电力英文翻译英文+中文
OVERFLOW SPILLWAYAn overflow spillway is a section of dam designed to permit water to pass over its crest. Overflow spillways are widely used on gravity, arch, and buttress dams. Some earth dams have a concrete gravity section designed to serve as a spillway. The design of the spillway for tow dams is not usually critical, and a variety of simple crest patterns are used. In the case of large dams it is important that the overflowing water be guided smoothly over the crest with a minimum of turbulence. If the overflowing water breaks contact with the spillway surface, a vacuum will form at the point of separation and cavitations may occur. Cavitations plus the vibration from the alternates making and breaking of contact between the water and the face of the dam may result in serious structural damage.Cavities filled with vapor, air, and other gases will form in a liquid whenever the absolute pressure of the liquid is close to the vapor pressure. This phenomenon, cavitations, is likely to occur where high velocities cause reduced pressure. Such conditions may arise if the walls of a passage are so sharply curved as to cause separation of flow from the boundary. The cavity, on moving downstream, may enter a region where the absolute is much higher. This causes the vapor in the cavity to condense and return to liquid with a resulting implosion, or collapse, extremely high pressure result. Some of the implosive activity will occur at the surfaces of the passage and in the crevices and pores of the boundary material. Under a continual bombardment of these implosions, the surface undergoes fatigue failure and small particles are broken away, giving the surface a spongy appearance. Thisdamaging action of cavitations is called pitting.The ideal spillway would take the form of the underside of the napped of a sharp-crested weir when the flow rate corresponds to the maximum design capacity of the spillway. More exact profiles may be found in more extensive treatments of the subject. The reverse curve on the downstream face of the spillway should be smooth and gradual; A radius of about one-fourth of the spillway height has proved satisfactory. Structural design of an ogee spillway is essentially the same as the design of a concrete gravity section. The pressure exerted on the crest of the spillway by the flowing water and the drag forces caused by fluid friction are usually small in parison with the other forces acting on the section. The change in momentum of the flow in the vicinity of the reverse curve may, however, create a force which must be considered. The requirements of the ogee shape usually necessitate a thicker section than the adjacent no overflow sections.A saving of concrete can be effected by providing a projecting corbel on the upstream face to control the flow in outlet conduits through the dam, a corbel will interfere with gate operation. The discharge of an overflow spillway is given by the weir equation23C Q Lh ω=Where Q=discharge, or sec /3m t coefficien C =ωL=coefficienth=head on the spillway (vertical distance from the crest of the spillway tothe reservoir level), mThe coefficient ωC varies with the design and head. Experimental models are often used to determine spillway coefficient. End contractions on a spillway reduce the effective length below the actual length L. Square-cornered piers disturb the flow considerably and reduce the effective length by the width of the piers plus about 0.2h for each pier.Streamlining the piers or flaring the spillway entrance minimizes the flow disturbance. If the cross-sectional area of the reservoir just upstream from the spillway is less than five times the area of flow over the spillway, the approach velocity with increase the discharge a noticeable amount. The effect of approach velocity can be accounted for by the equation2320g 2V h Q ⎪⎪⎭⎫ ⎝⎛+=L C ω where 0V is the approach velocity.PROPERTIES OF CONCRETEThe characteristics of concrete should be considered in relation to the quality for any given construction purpose. The closest practicable approach to perfection in every property of the concrete would result in poor economy under many conditions, and the most desirable structure is that in which the concrete has been designed with the correct emphasis on each of the various properties of the concrete, and not solely with a view to obtaining, say, the maximum possible strength.Although the attainment of the maximum strength should not be the sole criterionin design, the measurement of the crushing strength of concrete cubes or cylinders provides a means of maintaining a uniform standard of quality, and, in fact, is the usual way of doing so. Since the other properties of any particular mix of concrete are related to the crushing strength in some manner, it is possible that as a single control test it is still the most convenient and informative.The testing of the hardened concrete in prefabricated units presents no difficulty, since plete units can be selected and broken if necessary in the process of testing. Samples can be taken from some parts of a finished structure by cutting cores, but at consider one cost and with a possible weakening of the structure. It is customs, therefore, to estimate the properties of the concrete in the structure on the oasis of the tests made on specimensmounded from the fresh concrete as it is placed. These specimens are pacted and cured in a standard manner given in BS 1881 in 1970 as in these two respects it is impossible to simulate exactly the conditions in the structure. Since the crushing structure is also affected by the size and shape of a specimen or part of a structure, it follows that the crushing strength of a cube is not necessary the same as that of the mass of exactly the same concrete.Crushing strengthmm,or Concrete can be made having a strength in pression of up to about 80N/2 even more depending mainly on the relative proportions of water and cement, that is, the water/cement ratio, and the degree of paction. Crushing strengths ofmm at 28 days are normally obtained on the site with between 20 and 50 N/2reasonably good supervision, for mixes roughly equivalent to 1:2:4 of cement: sand: coarse aggregate. In some types of precast concrete such as railway sleepers,mm at 28 days are obtained with rich mixes strengths ranging from 40 to 65 N/2having a low water/cement ratio.The crushing strength of concrete is influenced by a number of factors in addition to the water/cement ratio and the degree of paction. The more important factors areType of cement and its quality. Both the rate of strength gain and the ultimate strength may be affected.Type and surface texture of aggregate. There is considerable evidence to suggest that some aggregates produce concrete of greater pressive and tensile strengths than obtained with smooth river gravels.Efficiency of curing. A loss in strength of up to about 40 per cent may result from premature drying out. Curing is therefore of considerable, importance both in the field and in the making of tests. The method of curing concrete test cubes given in BS 1881 should, for this reason, be strictly adhered to.Temperature In general, the rate of hardening of concrete is increased by an increase temperature. At freezing temperatures the crushing strength may remain low for some time.Age Under normal conditions increase in strength with age, the rate of increase depending on the type of cement with age. For instance, high alumina cement produces concrete with a crushing strength at 21 hours equal to that of normalPortland cement concrete at 28 days. Hardening continues but at a much slower rate for a number of years.The above refers to the static ultimate load. When subjected to repeated loads concrete fails at a load smaller than the ultimate static load, a fatigue effect.A number of investigators have established that after several million cycles of loading, the fatigue strength in pression is 50-60 per cent of the ultimate static strength.Tensile and flexural strengthThe tensile strength of concrete varies from one-eighth of the pressive strength at early ages to about one- twentieth later, and is not usually taken into account in the design of reinforced concrete structures. The tensile strength is, however, of considerable importance in resisting cracking due to changes in moisture content or temperature. Tensile strength tests are used for concrete roads and airfields.The measurement of the strength of concrete in direct tension is difficult and is rarely attempted. Two more practical methods of assessing tensile strength are available. One gives a measure of the tensile strength in bending, usually termed the flexural strength. BS 1881:1970 gives details concerning the making and curing of flexure test specimens, and of the method test. The standard size of specimen is 150mm×150mm×750mm long for aggregate of maximum size 40mm. If the largest nominal size of the aggregate is 20mm, specimens 100mm×100mm×750mm long may be used.A load is applied through two rollers at the third points of the span untilthe specimen breaks. The extreme fiber stresses, that is, pressive at the top and tensile at the bottom, can then be puted by the usual beam formulae. The beam will obviously fail in tension since the tensile strength is much lower than the pressive strength. Formulae for the calculation of the modulus of rupture are given in BS 1881:1970.Test specimens is the form of beams are sometimes used to measure the modulus of rupture or flexural strength quickly on the site. The two halves of the specimen may then be crushed so that besides the flexuralstrength the pressive strength can be approximately determined on the same sample. The test is described in BS 1881:1970.Values of the modulus of rupture are utilized in some methods of design of unreinforced concrete roads and runways, in which reliance is placed on the flexuralstrength of the concrete to distribute concentrated loads over a wide area.More recently introduced is a test made by splitting cylinders by pression across the diameter, to give what is termed the splitting tensile strength; Details of the method are given in BS 1881:1970.Values of the modulus of rupture are utilized in some methods of design of unreinforced concrete roads and runways, in which reliance is place on the flexural strength of the concrete to distribute concentrated loads over a wide area.More recently introduced is a test made by splitting cylinders by pression across the diameter, to give what is termed the splitting tensile strength; Details of the method are given in BS 1881:1970. the testing machine is fitted with anextra bearing bar to distribute the load along the full length of the cylinder Plywood strips, 12mm wide and 3mm thick are inserted between the cylinder and the testing machine bearing surfaces top and bottom.From the maximum applied load at failure the tensile splitting strength is calculated as follows:ld p2f t π=Where =t f splitting tensile strength, N/2mmP=maximum applied load in Nl=length of cylinder in mmd=diameter in mmAs in the case of the pressive strength, repeated loading reduces the ultimate strength so that the fatigue strength in flexure is 50-60 per cent of the static strength.Shear strengthIn 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. RESERVOIRSWhen 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.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.DistributionReservoirs.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 flood-mitigation 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 outflowreaches 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 sluice-way capacity to permit rapid drawdown before or after a flood.Types of flood control reservoirs. There are tow basic types of flood-mitigation 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 storage-reservoir, 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 hassubsided 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.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 evenat 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 floods and also to conserve water for water supply, irrigation, industrial needs, hydroelectric purposes, etc. shall be called a multipurpose reservoir.THE ELECTRIC POWER SYSTEMA great amount of effort is necessary to maintain an electric power supply within the requirement of the various types of customers served. Large investments are necessary, and continuing advancements in methods must be made as loads steadily increase from year to year. Some of the requirements for electric power supply are recognized by most consumers, such as proper voltage, availability of power on demand, reliability, and reasonable cost. Other characteristics, such as frequency, wave shape, and phase balance, are seldom recognized by the customer but are given constant attention by the utility power engineers.The voltage of the power supply at the customer’s service entrance must be held substantially constant. Variations in supply voltage are, from the customer’s view, detrimental in various respects. For example, below-normal voltage substantially reduces the light output from incandescent lamps. Above-normal voltage increase the light output but substantially reduces the life of the lamp. Motor operate at below-normal voltage draw abnormally high current and may overheat, even when carrying no more than the rated horsepower load. Over voltage on a motor may cause excessive heat loss in the iron of the motor, wasting energy and perhaps damaging the machine. Service voltages are usually specified by a nominal value and the voltage than maintained close to this value, deviating perhaps less than 5 percent above or below the nominal value. For example, in a 120-volt residential supply circuit, the voltage might normally vary between the limits of 115 and 125 volts as customer load and system conditions change throughout the day.Power must be available to the consumer in any amount that be may require from minute to minute. For example, motors may be turned on or off, without advance warning to the electric power pany. As electrical energy cannot be stored (except to a limited extent in storage batteries), the changing loads impose severe demands on the control equipment of any electrical power system. The operating staff must continually study load patterns to predict in advance those major load changes that follow known schedules, such as the starting and shutting down of factories at prescribed hours each day.The demands for reliability of service increase daily as our industrial and social environment bees more plex. Modern industry is almost locally dependent on electric power for its operation. Homes and office buildings are lighted, heated, and ventilated by electric power. In some instances loss of electric power may even pose a threat a life itself. Electric power, like everything else that is man-made can never be absolutely reliable. Occasional interruptions to service in limited areas will continue. Interruptions to large areas remain a possibility, although such occurrences may be very infrequent. Further interconnection of electric supply systems over wide areas, continuing development of reliable automated control systems and apparatus; provision of additional reserve facilities; and further effort in developing personnel to engineer, design, construct, maintain, and operate these facilities will continue to improve the reliability of the electric power supply.The cost of electric power is a prince consideration in the design and operation of electric power is a prime consideration in the design and operation of electric power system. Although the cost of almost all modities has risen steadily over the past many years, the cost per kilowatt-hour of electrical energy has actually declined. This decrease in cost has been possible because of improved efficiencies of the generating stations and distribution systems. Although franchises often grant the electric power pany exclusive rights for the supply of electric power to an area. There is keen petition between electric power and other forms of energy, particularly for heating and for certain heavy load industrial processes.The power supply requirements just discussed are all well known to most electric power users. There are, however, other specifications to the electric power supply which are so effectively handled by the power panies that consumers are seldom aware that such requirements are of importance.The frequency of electric power supply in the United States is almost entirely 60 hertz (formerly cycles per second). The frequency of a system is dependent entirely upon the speed at which the supply generator is rotated by its prime mover. Hence frequency control is basically a matter of speed control of the machines in the generating stations. Modern speed-control systems are very effective and hold frequency almost constant. Deviations are seldom greater than 0.02 hertz.In an ac system the voltage continually varies with time, at one instant being positive and a short time later being negative, going through 60 plete cycles of change in each second. Ideally a plot of the time change should be a sine wave.In poorly designed generating equipment, harmonics may be present and the wave shape may be somewhat. The presence of harmonics produces unnecessary losses in the customer’s equipment and sometime produces hum in nearby telephone lines. The voltage wave shape is basically determined by the construction of the generation equipment. The power panies put specification limitations on the harmonic content of generator voltages and so require equipment manufactures to design and build their machines to minimize from this effect. ENVIRONMENT POLLUTIONThe existence of pollution in the environment, as a national and a world problem,was not generally recognized until the 1960s.Today many people regard pollution as a problem that will not go away, but one that could get worse in the future. It is increasingly being appreciated that the general effects of pollution produce a deterioration of the quality of the environment. This usually means that pollution is responsible for dirty streams, rivers and sea shorts, atmospheric contamination, the dissociation of the countryside, urban dereliction, affecting the environment in which people reside, work, and spend their leisure time.The present increasing emphasis upon pollution may create the impression that there has been a relatively sudden deterioration of the environment, that was not apparent twenty or thirty years ago. This is not the case. Pollution must have started at the time when man began to use the natural resources of the environment for his own benefit. At he began to develop a settled life in small munities, the activities of clearing trees, building shelter, cultivating crops, and preparing and cooking food must have altered the natural environment. Later, as the human population increased and became concentrated into large munities which developed craft skills. There were increasing quantities of human and animal waste and rubbish to be disposed of in the early days of man’s existence the amount of waste was small. It was disposed of locally and had virtually no effect upon the environment. Later, when large human settlements and towns were established, waste disposal began to cause obvious pollution of streets and water courses. In the thirteenth century the prevalence of cholera, typhus, typhoid and bubonic plague was associated with the lack of proper waste disposal methods. By themed-nineteenthcentury the population of the UK had increased to 22 million, and many canals and rivers were grossly polluted with sewage and industrial waste. Some sewerage systems existed in towns, but the collected sewage was discharged into the nearest river without ant treatment. Salmon had pletely disappeared from the River Thames and outbreaks of cholera still occurred in London. A Royal mission on the Prevention of River Pollution was established in 1857, and eventually the first preventive river pollution legislation was passed in 1876 and 1890. However, there was little significant improvement in pollution until after the First World War, and the condition of rivers had deteriorated again by the end of the Second World War. Even today, a number of British and continental coastal towns discharge almost untreated sewage into near-shore waters.The increasing pollution of land water was acpanied by air pollution. This must have begun as soon as man started to use wood fires to provide ‘space hosting’and a means of cooking food. Later surface, soft coal was discovered and used as a fuel, and records shown that coal smokes was a nuisance in London in the thirteenth century. In 1273,Edward I made the first ever anti-pollution law to prevent the use of coal for domestic heating, so smoke pollution has been recognized for at least 700 years. However, smoke pollution in London continued and is recorded in both the sixteenth and seventeenth centuries. In the late eighteenth and throughout the nineteenth centuries there was a marked increase in air pollution, because of the greater use of coal by developing industry. From 1750, the chemical industry began to develop, and this caused the discharge of acid fumes into the smoky airof some manufacturing towns. A Royal mission was set up in 1862 to consider air pollution and this resulted in the first Alkali Act in 1863, which set limits to the concentration of acid in discharged waste gases. However, the increasing domestic and industrial bustion of coal, and the production of piped coal gas from 1815, caused air pollution to steadily get worse. Large cities were particularly affected, and the well known 5 day smog incident in London in 1952 directly contributed to the deaths of 4000 people. As a result, the Beaver mittee on Air Pollution was established in 1953, and the Clean Air Act was passed in 1956. This was the first effective statute to provide the means of controlling atmospheric pollution.Noise pollution probably started when man first developed machines. The increase in industrial plants in the nineteenth century produce indoor noise pollution of the working environment for many factory and mill workers over a 6 day week. Outdoors, the development of private and public transport bright environmental noise, as the railway services came into use during the 1830s, motor transport from 1900, and regular aero plane services from 1922. during the first half of the twentieth century environmental noise considerably increased, but it was not recognized as pollution. Industrial and outdoor noise was designated as ‘nuisance’when the Noise Abatement Act was passed in 1960. Whereas the earlier increase in noise occurred in work places and in connection with transport, during the past thirty years noise has spread into the home and places of leisure and entertainment. Certainly the most rapid increase in environmental pollution has。
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Design of SpillwaysSpillways are ordinarily classified according to their most prominentfeature .Commonly referred to types can be listed as follows.1. Free Overall (Straight Drop) SpillwaysA free overfall or straight drop spillways is one in which the flow drops freely from the crest. This type is suited to a thin arch or deck overflow dam or to a crest is which has a nearly vertical downstream face. Occasionally the crest is extended in the form of an overhanging lip to direct small discharges away from the face of the overfall section.Where no artificial protection is provided at the base of the overfall, scour will occur in most streambeds and will form a deep plunge poll. The volume and depth of the hole are related to the range of discharges, the height of the drop, and the depth of tailwater.A free overfall spillways is not adaptable for high drops on yielding foundations, because of the large impact forces which must be absorbed by the apron at the pointof impingement of the jet. Vibrations incident to the impact might crack or displace the structure, with danger from failure by piping or undermining. Ordinarily, the useof this structure for hydraulic drops from head pool to tailwater in excess of 20 feet should not be considered.2. Ogee (Overflow) SpillwaysThe ogee spillways has a control weir which is ogee or S-shaped in profile. The upper curve of the ogee ordinarily is made to conform closely to the profile of lower nappe of a ventilated sheet falling from a sharp-crested weir. Flow over the crest is made to adhere to the face of the profile by prevening access of air to the under sideof the sheet. For discharges at designed head, the flow glides over the crest with no interference from the boundary surface and attains near maximum discharge efficiency. The profile below the upper curve of the ogee is continued tangent along a slope to support the sheet on the face of the overflow. A reverse curve at the bottom of the slope turns the flow onto the apron of a stilling basin or into the spillway discharge channel.An ogee crest and apron may comprise all entire spillway, such as the overflow portion of a concrete gravity dam, or the ogee crest may only be the control structure for some other type of spillway. Because of its high discharge efficiency, thenappe-shaped profile is used for most spillway control crests.3. Side Channel SpillwaysThe side channel spillway is one in which the control weir is placed along the side of and approximately parallel to the upper portion of the spillway discharge channel. Flow over the crest falls into a narrow trough opposite the weir, turns an approximate right angle, and then continues into the main discharge channel.Discharge characteristics of a side channel spillway are similar to those of an ordinary overflow and are dependent on the selected profile of the weir crest. The discharge constriction may be a point of critical flow in the channel, an orifice control, or a conduit or tunnel flowing full. Although the side channel is neither hydraulically efficient nor inexpensive, it has advantages which make it adaptable to certainspillway layouts.4. Chute (Open Channel or Trough) SpillwaysA spillways, whose discharge is conveyed from the reservoir to the downstream river level through an open channel, placed either along a dam abutment or through a saddle, might be called a chute, open channel, or trough type spillway. These designations can apply regardless of the control device used to regulate the flow. Thus, a spillway having a chute-type discharge channel,though controlled by an overflow crest, a gated orifice, a side channel crest, or some other control device, might still be called a chute spillway. However, the name is most often applied when the spillway control is placed normal or nearly normal to the axis of an open channel, and where the streamlines of flow both above and below the control crest follow in the direction of the axis.The chute spillway has been used with earth fill dams more often than any other type. Factors influencing the selection of chute spillways are the simplicity of their design and construction, their adaptability to almost any foundation condition, and the overall economy often obtained by the use of large amounts of spillways excavationin the dam embankment.Chute spillways ordinarily consist of an entrance channel, a control structure, a discharge channel, a terminal structure, and an outlet channel. The simplest form of chute spillway has a straight centerline and is of uniform width. Often, either the axis of the entrance channel or that of the discharge channel must be curved to fit the alignment to the topography. In such cases,the curvature is confined to the entrance channel if possible, because of the low approach velocities. Where the discharge channel must be curved, its floor is sometimes superelevated to guide thehigh-velocity flow around the bend, thus avoiding a piling up of flow toward the outside of the chute.5. Conduit and Tunnel SpillwaysWhere a closed channel is used to convey the discharge around or under a dam, the spillway is often called a tunnel or conduit spillway, as appropriate. The closed channel may take the from of a vertical or inclined shaft, a horizontal tunnel through earth or roke, or a conduit constructed in open cut and backfilled with earth materials. Most forms of control structures,including overflow crest,vertical of inclined orifice entrances, drop inlet entrances, and side channel crests, can be used with conduit and tunnel spillways.With the drop inlet or orifice control, the tunnel or conduit size is selected so that it flows full for only a short section at the control and thence partly full for its remaining length. To guarantee free flow in the tunnel, the ratio of the flow area to the total tunnel area is often limited to about 75 percent. Air vents may be provided at critical points along the tunnel or conduit to insure an adequate air supply which will avoid unsteady flow through the spillway.Tunnel spillways may present advantages for dam sites in narrow canyons with steep abutments or at sites where there is danger to open channels from snow or rock slides. Conduit spillways may be appropriate at dam sites in wide valleys, where the abutments rise gradually and are at a considerable distance from the stream channel.Use of a conduit will permit the spillway to be located under the dam near the streambed.6. Drop Inlet (Shaft or Morning Glory) SpillwaysA drop inlet or shaft spillway, as the name implies, is one in which the water enters over a horizontally positioned lip, drops through a vertical or sloping shaft, and then flow to the downstream river channel through a horizontal or near horizontal conduit or tunnel. The structure may be considered as being made up of three elements; namely,an overflow control weir, a vertical transition,and a closed discharge channel. Where the inlet is funnel-shaped, this type of structure is often called a "morning glory" or "glory hole" spillway.Discharge characteristics of the drop inlet spillway may vary with a range of head. For example, as the heads increase on a glory hole spillway, the control will shift from weir flow over the crest to tube flow in the transition and then to full pipe flow in the downstream portion. A drop inlet spillway can be used advantageously at dam sites in narrow canyons where the abutments rise steeply or where a diversion tunnel or conduit is available for use as the downstream leg. Another advantage of this type of spillway is that near maximum capacity is attained at relatively low heads.7. Siphon SpillwaysA siphon spillway is a closed conduit system formed in the shape of an inverted U, positioned so that inside of the bend of the upper passageway is at normal reservoir storage level. The initial discharges of the spillway, as the reservoir level rises above normal, are similar to flow over a weir. Siphonic action takes place after the air in the bend over the crest has been exhausted. Continuous flow is maintained by the suction effect due to the gravity pull of the water in the lower leg of the siphon.The principal advantage of a siphon spillway is its ability to pass full capacity discharges with narrow limits of headwater rise. A further advantage is its positive and automatic operation without mechanical devices or moving parts.设计溢洪道溢洪道设计溢洪道通常分类根据其最突出的特征。