專業(yè)外語-水工部分課件

1、Lesson 11 dams 壩The first dam for which there are reliable records was built on the Nile River sometime before 4000B.C. it is used to divert the Nile and provide a site for the ancient city of Memphis. 據(jù)可靠記載，世界上第一座壩是公元前4000年以前在尼羅河上修建的。他使尼羅河改道，并為古老的孟菲斯城提供城址。The oldest dam still in use is the Almanza

2、Dam in Spain, which was constructed in the sixteenth century. With the passage of time, materials and methods of construction have improved, making possible the erection of such large dams as the Nurek Dam which is being constructed in the Former Soviet Union on the Vaksh River near the border of Af

3、ghanistan. This dam will be 1017 ft (333m)high,of earth and rock fill. 至今仍在使用的最古老的壩是16世紀修建的西班牙阿爾曼扎壩。隨著歲月的流逝，各種建筑材料和施工方法得到了改善，修建列努克這樣的大壩才成為可能。該壩正在前蘇聯(lián)境內(nèi)靠近阿富汗邊界的瓦赫什河上施工，是一座高達1017英尺（333米）的土石壩。The failure of a dam may cause serious loss of life and property; consequently, the design and maintenance of da

4、ms are commonly under government surveillance. In the United States over 30,000 dams are under the control of state authorities. The 1972 Federal Dam Safety Act (PL 92-267)requires periodic inspections of dams by qualified experts. The failure of the Teton Dam in Idaho in June 1976 added to the conc

5、ern for dam safety in the United States. 大壩失事可能造成生命財產(chǎn)的嚴重損失。因此，壩的設計和維修通常是在政府監(jiān)督下進行的。美國有3萬多座壩由各州政府控制著。1972年（美國）聯(lián)邦大壩安全法（PL92-367）規(guī)定，必須由合格的專家對大壩進行定期檢查。在1976年6月愛達荷州提堂大壩失事后，美國對大壩安全更為關切。1 types of dams 壩的類型Dams are classified on the basis of the type and materials of construction, as gravity, arch, buttress

6、, and earth. The first three types are usually constructed of concrete. A gravity dam depends on its own weight for stability and is usually straight in plan although sometimes slightly curved. Arch dams transmit most of the horizontal thrust of the water behind them to the abutments by arch action

7、and have thinner cross section than comparable gravity dams. Arch dams can be used only in narrow canyons where the walls are capable of withstanding the thrust produced by the arch action. The simplest of the many types of the buttress dams is the slab type, which consists of sloping flat slabs sup

8、ported at intervals by buttress. Earth dams are embankments of rock or earth with provision for controlling seepage by means of an impermeable core or upstream blanket. More than one type of dam may be included in a single structure. Curved dams may combine both gravity and arch action to achieve st

9、ability. Long dams often have a concrete river section containing spillway and sluice gates and earth or rock-fill wing dams for the remainder of their length. 壩按其形式和建筑材料分為：重力壩、拱壩、支墩壩和土壩。前三種壩通常是用混凝土澆筑的。重力壩依靠自重維持穩(wěn)定，通常在平面上呈直線狀，不過有時也略帶弧形。 拱壩通過拱的作用把水的水平推力中的大部分傳給地基，因此它的橫截面比重力壩單薄些。拱壩只用于崖壁能承受拱作用所產(chǎn)生的推力的峽谷中。

10、各種支墩壩中最簡單的是平板壩，它是由許多支墩間隔地支撐著傾斜的面板。土壩是一種由土或石料填筑而成并借助于不透水的心墻或上游鋪蓋防滲透的土堤。在一座大壩的結(jié)構中可包含不止一種壩型?；⌒螇慰梢园阎亓ψ饔煤凸白饔媒Y(jié)合起來，以利壩的穩(wěn)定。長壩常常有一個包括溢洪道、泄水閘在內(nèi)的混凝土壩段，其余壩段是用土或石填筑的副壩。The selection of the best type of dam for a given site is a problem in both engineering feasibility and cost, Feasibility is governed by topograp

11、hy, geology and climate. For example, because concrete spalls when subjected to alternate freezing and thawing, arch and buttress dams with thin concrete sections are sometimes avoided in areas subject to extreme cold. The relative cost of the various types of dams depends mainly on the availability

12、 of construction materials near the site and the accessibility of transportation facilities. Dams are sometimes built in stages with the second or later stages constructed a decade or longer after the first stage. 對于既定的壩址選擇最佳壩型是一個關系到工程可行性及其造價的問題。工程可行性受地形、地質(zhì)及氣候條件所支配。例如：由于混凝土遭受凍融作用的交替影響而引起剝落，因此在低溫地區(qū)常避

13、免采用斷面單薄的混凝土拱壩或支墩壩。各類壩的造價主要取決于能否在工地附近取得建筑材料和各種運輸工具能否進入。大壩有時分期建造，第二期或以后各期工程，往往在第一期以后需要10年或更長的時間。The height of a dam is defined as the difference in elevation between the roadway, or spillway crest, and the lowest part of the excavated foundation. However, figures quoted for heights of dams are often d

14、etermined in other ways. Frequently the height is taken as the net height above the old river bed.壩高定義為路面或溢洪道頂與基坑最低點之間的高程差。不過，引用的壩高值常常是用另外的一些方法確定的，往往取原河床以上的凈高度作為壩高。2 forces on dams 作用在壩上的力A dam must be relatively impervious to water and capable of resisting the forces acting on it. The most importan

15、t of these forces are gravity (weight of dam), hydrostatic pressure, uplift, ice pressure, and earthquake forces. These forces are transmitted to the foundation and abutments of the dam, which react against the dam with an equal and opposite forces, the foundation reaction. The effect of hydrostatic

16、 pressure caused by sediment deposits in the reservoir and of dynamic forces caused by water flowing over the dam may require consideration in special cases. 壩必須是相對不透水的，并能經(jīng)受得住作用在這上面的各種力。這些作用力中最重要的是重力（壩體重量）、靜水壓力、揚壓力、冰壓力及地震力。這些力傳給壩基和壩座，而壩基和壩座則對壩體產(chǎn)生一個大小相等方向相反的基礎反力。某些特殊情況下還要考慮水庫中沉積泥沙引起的靜水壓力的影響以及壩頂溢流所產(chǎn)生的

17、動力作用。The weight of a dam is the product of its volume and the specific weight of the material. The line of action of this force passes through the center of mass of the cross section. Hydrostatic forces may act on both the upstream and downstream faces of the dam. The horizontal component of the hyd

18、rostatic force is the force on a vertical projection of the face of the dam, and for unit width of dam it is Where: is the specific weight of water; is the depth of water. The line of action of this force is above the base of the dam. The vertical component of the hydrostatic force is equal to the w

19、eight of water vertically above the face of the dam and passes through the center of gravity of this volume of water.壩的自重是其體積和材料比重的乘積。該力的作用線通過橫剖面的形心。靜水壓力可同時作用在壩的上游面和下游面。靜水壓力的水平分力 是作用在壩面垂直投影上的力，對于單位寬度壩體而言其值為； 式中： 為水的比重； 是水深；該力的作用線在壩基以上 處。靜水壓力的豎直分力等于壩面正上方的水重，并通過該水體的重心。Water under pressure inevitably f

20、inds its way between the dam and its foundation and creates uplift pressures. The magnitude of the uplift force depends on the character of the foundation and the construction methods. It is often assumed that the uplift pressure varies linearly from full hydrostatic pressure at the upstream face (h

21、eal ) to full tail-water pressure at the downstream face (toe). For this assumption the uplift force is Where; is the base thickness of the dam; and are the water depths at the heel and toe of the dam, respectively. The uplift force will act through the center of area of the pressure trapezoid (fig.

22、11.1)處于壓力作用下的水必然要在壩和壩基之間流動，因而產(chǎn)生了揚壓力。揚壓力的大小取決于基礎的特性和施工方法。經(jīng)常假定揚壓力從上游面（壩踵）處的全部靜水壓力直線變化到下游面（壩趾）處的全部尾水壓力。根據(jù)這一假設，揚壓力 為 式中： 是壩基的寬度； 和 分別是壩踵和壩趾處的水深。揚壓力的作用線通過壓力梯形的形心（圖11.1）Figure 11.1 free-body diagram of the cross section of a gravity damActual measurements on dams (figure11.2) indicate that the uplift forc

23、e is much less than that given by eq.11.2. Various assumptions have been made regarding the distribution of uplift pressures. The U.S. Bureau of Reclamation sometimes assumes that the uplift pressure on gravity dams varies linearly from two-thirds of full uplift at the heel to zero at the toe. Drain

24、s are usually provided near the heel of the dam to permit the escape of seepage water and relieve uplift.一些壩的實測資料表明（圖11.2）；揚壓力比公式11.2所給出的值小得多。對揚壓力的分布有各種不同的假設，美國墾務局認為重力壩的揚壓力成直線變化，在壩踵處為全部揚壓力的2/3，到壩趾處為零。壩踵附近通常設有排水裝置，以便排除滲流水量，減小揚壓力。Figure.11.2 maximum observed uplift pressure under some existing gravity

25、 dams (Data from the ASCE Committee on Uplift in Masonry dams- ASCEabbr.American Society of Civil Engineers 美國土木工程師協(xié)會)Lesson 12 embankment dams 土石壩1 selection of embankment type 土石壩壩型的選擇In general, there are two types of embankment dams: earth （earthfill dam） and rockfill（rock fill dam）. The selecti

26、on 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 eas

27、ily 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. 一般來說，土石壩有兩種類型：土壩和堆石壩。壩型的選擇取決于能從需要開挖的地點和可用的料場（料場 stock ground）（borrow area 取土面積; 采料場）處取得合用材料的情況。應當指出的是（注意），根據(jù)巖石的物理特性，堆石可以

28、逐漸變化為填土，因而不能對土石料作出嚴格而固定的分類。那些軟弱的和在開挖填筑時容易破碎的巖石可被歸入填土類。而堅硬和不會大量破碎的的巖石，則列為堆石類。The selection and the design of an earth embankment are based upon the judgement and experience of the designer and is to a large extent of an empirical nature. The various methods of stability and seepage analysis are used

29、mainly to confirm the engineers judgement.一座土壩的選定和設計都有賴于設計人員的判斷和經(jīng)驗，而且在很大程度上是屬于經(jīng)驗性的。各種穩(wěn)定和滲透分析方法，主要是作為證實工程師的判斷而使用的。2 freeboard 超高 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, a

30、nd 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 completion of the embankment.所有的土壩都必須有一個足夠的額外高度，稱為超高，以防止水庫漫頂。超高的高度必須足以在波浪作用、風浪壅高和地震影響下，不會導致壩的漫頂。除了超高外，對于壩建成時發(fā)

31、生的壩體和地基沉陷，還必須在高度上留有余地。3 top width 壩頂寬度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 massiv

32、e landslides in the pool or by seismic block tipping, then extra top width of erosion resistive fill will be required.土壩的壩頂寬度一般用常規(guī)設備便于施工的填筑寬度來控制。通常，壩頂寬度應不小于30英尺。如果存在著大規(guī)模塌方進入水庫，或者有因地震使巖塊倒落而引起波浪漫頂?shù)奈ｋU，則需要采用抗沖刷的材料填筑更寬的壩頂高度。4 alignment 定線The alignment of an earthfill dam should be such as to minimize con

33、struction 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 giv

34、en an alignment which is arched upstream so that deflections of the embankment under pool load will put the embankment in compression thus minimizing transverse cracking.土壩的壩軸線選定應盡量使建設費用降到最少，但是也不能因此引起壩體發(fā)生滑動或開裂。一般來說，一條橫跨河谷的最短的直線，可能滿足要求。但是，當?shù)氐牡匦魏偷鼗鶙l件可能要求采用另外的方案。對于峽谷的壩，常采用向上游拱出的壩軸線，以便在壩體受庫水壓力作用而發(fā)生變形時，能

35、使壩體壓緊，從而盡量減少其橫向開裂。5 Abutments 兩岸壩座Three problems are generally associated with the abutments of earth dams: seepage, instability, and transverse cracking of the embankment. If the abutment consists of deposits of pervious soils it may be necessary to construct an upstream impervious blanket and down

36、stream drainage measures to minimize and control abutment seepage.一般有三個問題與土壩壩座有關：滲透；不穩(wěn)定；壩體的橫向開裂。如果壩座是由透水的沉積土構成，就可能需要建造一道上游不透水的鋪蓋和下游排水設施，可盡量減少和控制壩座內(nèi)的滲透。 Where steep abutments exist, especially with sudden changes of slopes or with steep bluff, there exists a danger of transverse cracking of the emban

37、kment fills. This can be treated by excavation of the abutment to reduce the slope, especially in the impervious and transition zones. The transition zones, especially the upstream, should be constructed of fills which have little or no cohesion and a well-distributed gradation of soils which will p

38、romote self-healing should transverse cracking occur.在壩座岸坡很陡的地方，特別在邊坡突變或有陡壁處，那里的壩體填土會產(chǎn)生橫向裂縫的危險。這個問題可以用開挖壩座放緩邊坡來處理，這樣的處理在不透水區(qū)和過渡區(qū)特別需要。過渡區(qū)，尤其是在上游側(cè)的過渡區(qū)，必須用粘著力很小或無粘著力且顆粒級配良好的土料來填筑，這種土料如發(fā)生橫向裂縫時能自行愈合。6 stage construction 分期施工It is often possible, and in some cases necessary, to construct the dam embankmen

39、t in stages. Factors dictating such a procedure are: a wide valley permitting the construction of the diversion or outlet works and part of the embankment at the same time; a weak foundation requiring that the embankment not be built too rapidly to prevent overstressing the foundation soils ; a wet

40、borrow area which requires a slow 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 blanket.土壩的分期施

41、工往往是可能的，而且在一些情況下是必須的。要求這樣施工程序的因素是：河谷寬闊，可以允許導流或泄水工程與一部分壩體同時施工；地基軟弱，要求壩體不要過快填筑，以防止地基中產(chǎn)生過大的應力；料場潮濕，要求放慢施工，以使土料能通過固結(jié)作用來增加抗剪強度。在某些情況下，可以需要增設基礎排水設施或填筑排水沙井，或采用水平透水的排水鋪蓋。7 Embankment soils 壩體的土料Most soils are suitable for use for embankment construction, however, there are physical and chemical limitations,

42、 soils which contain excessive salts or other soluble materials should not be used. Substantial organic content should not exist in the soils. Lignite sufficiently scattered through the fill to prevent the danger of spontaneous combustion, is not objectionable. Fat clays with high liquid limits may

43、prove difficult to work and should be avoided.大多數(shù)土料適合于壩體填筑，然而，在物理和化學性質(zhì)上也有一定的局限，含有過多鹽和可溶性物質(zhì)的土料，不可以使用。在土壤里不應存在大量的有機質(zhì)成分。褐煤若能通過填筑而充分分散，無自然之虞，就不妨礙使用。而具有高度流限的肥粘土，多半難以施工，必須避免使用。8 Compaction requirements壓實的要求The strength of the impervious and semi-impervious soils depends upon the compacted densities. These

44、 depend in turn upon the water content and weight of the compacting equipment. The design of the embankment is thus influenced by the water content of the borrow soils and by the practicable alternations to the water content either prior to placement of the fill or after placement but prior to rolli

45、ng. 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 placemen

46、t 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 compacted to at least 80 percent of relative density.不透水和半透水的土料的強度取決于壓實的密度。壓實密度又取決于土料的含水量和壓實設備的重量。因此，料場土料的含水量和在填筑前或堆筑后而未碾壓前的填土實際含水量的變化，都會影響壩體的填筑。如果天然含水量太高，可

47、以在料場用排水或?qū)⑼亮习宜傻霓k法來減低。如果土料太干燥，則需在料場用灑水和泡水的辦法把土料潤濕，然后再讓土料在使用以前保持穩(wěn)定的含水量。填筑時的含水量范圍一般介于比標準普氏最優(yōu)含水量低2%到高2%3%之間。透水性土料至少壓實到相對密度的80%。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 abutmen

48、t, the fill must be placed in thin lifts and compacted by mechanical hand tampers. All overhangs should either be removed or filled with lean concrete prior to fill placement.如果需要，應該變換填筑層的含水量、鋪層厚度、碾壓遍數(shù)和碾壓機的型式等，進行填筑試驗。對于坡度很陡的壩座部位，必須用薄層填筑，并用手扶打夯機夯實。所有外懸突出部位，均應在填土堆筑以前挖除或用貧混凝土填平。9 types of instruments觀測

49、儀器的類型 The type of instrumentation depends upon the size and complexity of the project. The devices in common use are: piezometers ; surface movement monuments ; settlement gages ; inclinometers ; internal movement and strain indicators ; pressure cells ; seismic acceleration meter ；movement indicato

50、rs at conduit joints and other concrete structures觀測儀器的類型取決于工程的規(guī)模和復雜性。通用的裝置是：測壓計； 表面位移標志；沉陷量測儀（計）；測斜儀；內(nèi)部位移和應變指示儀；壓力盒（壓力傳感器或壓應力計）；地震加速度儀；在管道接頭和其他混凝土結(jié)構上的位移標志。Lesson 13 concrete gravity dam on rock foundations 巖基上的混凝土重力壩The designer of any dam must make basic assumptions regarding site conditions and t

51、heir effects on the proposed structure. 設計人員在設計任何壩時，都必須對有關壩址的情況及其對結(jié)構物的影響做出一些基本假定。Site investigations provide the engineer with much of the information to evaluate these assumptions, the bases for safe dam design. 壩址的查勘為工程師擬定這些假定提供了許多資料。這些假定是安全設計的基礎。Some important assumptions for small dam design inv

52、olve uplift pressure, seepage control measures, channel degradation and downstream toe erosion, foundation conditions, and quality of construction. 有關小壩設計的一些主要假定包括：揚壓力，滲流控制措施，河槽沖刷深度以及下游壩趾的沖蝕，壩基條件和施工質(zhì)量。Additional assumptions should involve silt loads, ice pressures, earthquake accelerations, and wave

53、 forces.其它一些附加假定應包括泥沙荷載、冰壓力、地震加速度和波浪力。1 safety factors 安全系數(shù)Safety factors should be considered in the light of economic conditions. Large safety factors result in a more costly structure; however, low safety factors may result in failure, which could also lead to high cost.安全系數(shù)應根據(jù)經(jīng)濟情況來考慮。安全系數(shù)大，導致結(jié)構費

54、用昂貴；而安全系數(shù)小則可能引起失事，也會導致很大的經(jīng)濟損失。Proper safety factors result only from an adequate determination of sliding, overturning, and overstressing forces within and acting on the dam.只有在適當?shù)卮_定壩內(nèi)和作用在壩體上的滑動、傾覆以及應力超限的作用力之后，才能得到合適的安全系數(shù)。2 overturning傾覆Ordinarily, the safety factor against overturning is between 2

55、and 3. 一般來說（通常），抗傾覆安全系數(shù)在23之間。In small dams it is often larger.較小的壩通常取較大的值If the computed safety factor falls below 2, the section of the dam should be modified to increase the safety margin. 如果算出的安全系數(shù)小于2（在2以下），應修改壩的斷面以提高安全度。A gravity dam rarely fails from overturning since any tendency to overturn p

56、rovides greater opportunity for a sliding force to create the failure. 重力壩很少因傾覆而破壞。因為任何一種傾覆的趨勢，都更可能引起滑動而導致破壞。The safety factor against overturning is the ration of the righting moment to the overturning moment about the toe of the dam. This can be expressed as Which： is force due to weight of concre

57、te; is force due to weight or water on inclined surfaces; is force of water acting to displace dam downstream; is uplift force; is length of moment arm for respective forces.抗傾覆安全系數(shù)是繞壩址的復位力矩（扶正力矩restoring couple）和傾覆力矩的比值，可以用公式表示為： 式中： 為混凝土的重量； 為斜面上的水重； 為水對壩體向下游的推力； 為揚壓力； 為各力的力臂。Also, if the uplift p

58、ressure at the upstream face exceeds the vertical stress at any horizontal section without uplift, the uplift forces greatly increase the tendency for overturning about the downstream toe at that assumed horizontal plane.此外，如果上游面的揚壓力超過任一水平斷面上不計揚壓力算得的垂直應力，則揚壓力將使繞壩所假定的水平斷面下游點傾覆趨勢大大增加。The dam may still

59、 be considered safe if the tension stresses developed are less than the allowable stresses in the concrete and in the foundation material. This assumption is based on good workmanship and development of a tensile strength within the structure on all horizontal planes.在這種情況下，如果引起的拉應力小于混凝土內(nèi)和地基材料的允許應力，則該壩仍可認為是安全的。這個假定是基于施工工藝良好和結(jié)構內(nèi)所有平面上都具有抗拉強度做出的。3 sliding 滑動Three approaches are used by engineers in evaluating the safety