混凝土大壩外文翻譯--混凝土重力壩的設計分析與比較

1、<p><b>　　中文3018字</b></p><p>　　Comparison of Design and Analysis of Concrete Gravity Dam</p><p><b>　　ABSTRACT</b></p><p>　　Gravity dams are solid concret

2、e structures that maintain their stability against design loads from the geometric shape, mass and strength of the concrete.The purposes of dam construction may include navigation, flood damage reduction,hydroelectric po

3、wer generation, fish and wildlife enhancement,water quality,water supply,and recreation.The design and evaluation of concrete gravity dam for earthquake loading must be based on appropriate criteria that reflect both the

4、 desired level of safety and t</p><p>　　Keywords: Comparison Concrete Gravity Dam Dam Failure Design Earthquake Intensity Perturbation Stability and Stress </p><p>　　1.Introduction</p>

5、;<p>　　Basically, a gravity concrete dam is defined as a structure,which is designed in such a way that its own weight resists the external forces. It is primarily the weight of a gravity dam which prevents it fro

6、m being overturned when subjected to the thrust of impounded water [1]. This type of structure is durable, and requires very little maintenance. Gravity dams typically consist of a non overflow section(s) and an overflow

7、 section or spillway. The two general concrete construction methods for co</p><p>　　However, concrete gravity dams are preferred these days and mostly constructed. They can be constructed with ease on any da

8、m site, where there exists a natural foundation strong enough to bear the enormous weight of the dam. Such a dam is generally straight in plan, although sometimes, it may be slightly curve. The line of the upstream face

9、of the dam or the line of the crown of the dam if the upstream face in sloping, is taken as the reference line for layout purposes, etc. and is known as the </p><p>　　A typical cross-section of a high concre

10、te gravity dam is shown in Figure . The upstream face may be kept throughout vertical or partly slanting for some of its length. A drainage gallery is generally provided in order to relieve the uplift pressure exerted b

11、y the seeping water.Purposes applicable to dam construction may include navigation, flood damage reduction, hydroelectric power generation, fish and wildlife enhancement, water quality, water supply, and recreation.</

12、p><p>　　Many concrete gravity dams have been in service for over 50 years, and over this period important advances in the methodologies for evaluation of natural phenomena hazards have caused the design-basis e

13、vents for these dams to be revised upwards. Older existing dams may fail to meet revised safety criteria and structural rehabilitation to meet such criteria may be costly and difficult. The identified causes of failure,

14、based on a study of over 1600 dams [4] are: Foundation problems (40%), Inadequ</p><p><b>　　2.Loads </b></p><p>　　In the design of gravity concrete, it is essential to determine the l

15、oads required in the stability and stress analyses. The forces which may affect the design are: 1) Dead load or stabilizing force; 2) Headwater and tailwater pressures; 3) Uplift; 4) Temperature; 5) Earth and silt pressu

16、res; 6) Ice pressure; 7) Earth quake forces; 8) Wind pressure; 9) Subatmospheric pressure; 10) Wave pressure, and 11) Reaction of foundation. </p><p>　　The seismic safety of such dams has been a serious conc

17、ern since damage to the Koyna Dam in India in 1967 which has been regarded as a watershed event in the development of seismic analysis and design of concrete gravity dams all over the world. It is essential that those re

18、sponsible must implement policies and proce dures to ensure seismic safety of dams through sound professional practices and state-of-the-art in related technical areas. Seismic safety of dams concerns public safety and t

19、heref</p><p>　　2.1. Water Pressure </p><p>　　Water pressure (P) is the most major external force acting on gravity dams. The horizontal water pressure exerted by the weight of water stored on th

20、e upstream and downstream sides of the dam can be estimated from the rule of hydrostatic pr essure distribution and can be expressed by </p><p>　　where, H is the depth of water and is the unit weight of wate

21、r. </p><p>　　2.2. Uplift Pressure </p><p>　　Water seepage through the pores, cracks and fissures of the foundation materials, and water seepage through dam body and then to the bottom through th

22、e joints between the body of the dam and its foundation at the base exert an uplift pressure on the base of the dam. According to the [6], the uplift pressure intensities at the heel and toe of the dam should be taken eq

23、ual to their respective hydrostatic pressures and joined the intensity ordinates by a straight line. When drainage galleries are p</p><p>　　2.3. Earthquake Forces </p><p>　　An earthquake produce

24、s waves, which are capable of shaking the earth upon which the gravity dams rest, in every possible direction. The effect of an earthquake is, therefore, equivalent to imparting acceleration to the foundations of the da

25、ms in the direction in which the wave is traveling at the moment. </p><p>　　Generally, an earthquake induces horizontal acceleration (h) and vertical acc eleration (v). The values of these accelerations are

26、generally expressed as per centage of the acceleration due to gravity (g), i.e.,= 0.10 g or 0.20 g, etc. On an average, a value of ? equal to 0.10 to 0.15 g is generally sufficient for high dams in seismic zones. In ext

27、remely seismic regions and in conservative Designs even a value up to 0.30 g may sometimes be adopted [7]. </p><p>　　Earthquake loadings should be checked for horizontal as well as vertical earth quake accel

28、erations. While earthquake acceleration might take place in any direc tion,the analysis should be performed for the most unfavorable direction. </p><p>　　The earthquake loadings used in the design of concret

29、e gravity dams are based on design earthquakes and sitespecific motions determined from seismological eva luation. At a minimum, a seismological evaluation should be performed on all pro jects located in seismic zones 1

30、, 2, and 3 of Bangladesh [8], depending upon the severity of earthquakes. </p><p>　　The seismic coefficient method of analysis should be used in determining the resultant location and sliding stability of da

31、ms. In strong seismicity areas, a dynamic seismic analysis is required for the internal stress analysis. </p><p>　　2.3.1. Effect of Vertical Acceleration (ɑv) </p><p>　　A vertical acceleration m

32、ay either act downward or upward. When it acts in the upward direction, then the foundation of the dam will be lifted upward and becomes closer to the body of the dam, and thus the effective weight of the dam will increa

33、se and hence, the stress developed will increase. </p><p>　　When the vertical acceleration acts downward, the foundation shall try to move downward away from the dam body; thus, reducing the effective weight

34、 and the stability of the dam, and hence is the worst case for design. The net effective weight of the dam is given by </p><p><b>　　(2)</b></p><p>　　where, W is the total weight of t

35、he dam, kv is the fraction of gravity adopted for vertical acceleration, such as 0.10 or 0.20, etc. </p><p>　　In other words, vertical acceleration reduces the unit weight of the dam material and that of wa

36、ter to (1 – kv) times their original unit weights. </p><p>　　2.3.2. Effects of Horizontal Acceleration (ɑh) </p><p>　　The horizontal acceleration may cause 1) hydrodynamic pressure, and 2) horiz

37、ontal inertia force. </p><p>　　Hydrodynamic Pressure: Horizontal acceleration acting towards the reservoir causes a momentary increase in the water pressure, as the foundation and dam acc elerate towards the

38、 reservoir and the water resists the movement owing to its ine rtia. According to [9], the amount of this hydrodynamic force (Pe) is given by</p><p><b>　　(3)</b></p><p>　　where, Cm =

39、 maximum value of pressure coefficient for a given constant slope = 0.735(0θ/ 90) θ , whereθis the angle in degree, which the upstream face of the dam makes with the horizontal; kh = fraction of gravity adopted for horiz

40、ontal acceleration such as αh=kh×g </p><p>　　The moment of this force about the base is given by </p><p><b>　　(4)</b></p><p>　　2) Horizontal Inertia Force: In addi

41、tion to exerting the hydrodynamic pressure, the horizontal acceleration produces an inertia force into the body of the dam. This force is generated to keep the body and the foundation of the dam together as one piece. T

42、he direction of the produced force will be opposite to the accele ration imparted by the earthquake. </p><p>　　Since an earthquake may impart either upstream or downstream acceleration, it is needed to choos

43、e the direction of this force in the stability analysis of dam structure in such a way that it produces most unfavorable effects under the consid ered conditions. For example, when the reservoir is full, this force will

44、produce worst results if it is additive to the hydrostatic water pressure, thus Acting towards the downstream (i.e., when upstream earthquake acceleration towards the reservoir is prod</p><p>　　原文出自：http://w

45、ww.scirp.org/journal/PaperInformation.aspx?paperID=18185</p><p>　　混凝土重力壩的設計分析與比較</p><p><b>　　摘要</b></p><p>　　重力壩是一種堅實的混凝土結構.大壩建設的目的可能包括通航,減少洪水造成的損失,水力發(fā)電,魚類和野生動物養(yǎng)殖,蓄水灌溉等.

46、混凝土重力壩的設計和評估地震荷載必須基于適當?shù)臉藴?既能反映所需的安全級別，也要有設計的選擇和評價程序.在孟加拉國,整個國家被分成3個地震帶,這取決于地震強度的嚴重性.因此,本研究的主要目的是設計基于U.S.B.R高混凝土重力壩.在孟加拉國地震帶二區(qū),建議對不同水平地震強度從0.10g～0.30g和0.50g增量考慮地震烈度，持續(xù)的不確定性和嚴重程度等其他來設計負荷。并采用二維分析重心法和有限元法分析其穩(wěn)定性和應力條件。水平地震烈度擾動

47、的結果表明，穩(wěn)定力矩被發(fā)現(xiàn)，而處理USBR結果與水平地震強度的增量顯示應減少推薦的初始壩段，說明危及大壩穩(wěn)定性，提供這樣大的壩段，以增加穩(wěn)定力矩，減少安全故障。垂直使用ANSYS5.4分析獲得的剪切應力與使用二維重心法得到的比較，發(fā)現(xiàn)比較少，以2D重心法，除了在重力壩0.10g壩趾主應力-0.15g。雖然很明顯，利用ANSYS5.4分析較小壩段可能有足夠的應力，但這將是不可能讓較小堤壩部分的安全得到足夠的保障。在穩(wěn)定性分析中可以觀察到，

48、</p><p>　　關鍵詞：比較 混凝土重力壩 潰壩 設計 地震強度 穩(wěn)定和應力</p><p><b>　　介紹</b></p><p>　　一般來說，重力混凝土壩被定義為通過利用自重來達到抵抗外力這一目的一個混凝土結構，。重力壩主要的重量在承受的蓄水推力[1]下可以防止它被推翻。這種類型的結構是非常耐用的，并且只需要很少的維護。重

49、力壩通常由非溢流壩段（S）和溢流壩段或溢洪道組成。這兩種一般混凝土施工方法在混凝土重力壩是為常規(guī)放置大體積混凝土和碾壓混凝土。在古代重力壩一般由石頭砌筑，最常見于埃及，希臘和羅馬帝國。</p><p>　　然而，混凝土重力大壩是最近大多修建的首選。他們可以輕松在任何壩址構造，其中存在一個天然地基強大到足以承受大壩的巨大重量。這樣的大壩一般是直的，雖然有時它可能是略微彎曲。大壩或上游面的壩的冠部的線的上游面的傾斜線

50、，被取為用于布局的基準線，而被稱為“基線大壩”或“大壩軸”。當在合適條件的情況下，這樣的大壩可以被構建很高的高度。底座的寬度和重力壩高度之比一般小于1:1。</p><p>　　高混凝土重力壩的典型橫截面正如圖所示，它的上游面可能與大壩的某段長度保持垂直或部分傾斜。排水道一般是用來減緩滲出水所產(chǎn)生的浮力，大壩建設的適用性目的包括航行、降低洪水損失、水力發(fā)電、魚類和野生動物的養(yǎng)殖、水質(zhì)、控制供水量和娛樂。

51、 </p><p>　　很多混凝土重力壩的使用壽命為50年，在這期間自然現(xiàn)象災害估值方法的重大進步也讓堤壩設計數(shù)據(jù)需要隨之修改。更早存在的堤壩沒有改進安全標準和結構修復，因為這樣的標準是花費過多而且過程艱辛。一項對1600多個堤壩的研究找到了主要原因：基礎問題40%，泄洪口不足23%， 劣質(zhì)工程12%，下沉不勻10%，較高的壓力差5%，戰(zhàn)亂3%，路堤下滑2%，有缺陷的材料2%，操作上的失誤2%，和

52、地震1%。其他關于潰堤的調(diào)查被引用，而基于這些調(diào)查有人估計潰堤率從每年的到了。</p><p><b>　　2 負載</b></p><p>　　在混凝土重力壩的設計中，準確計算出荷載的穩(wěn)定性和壓力力分析是非常重要的?？赡苡绊懺O計的因素是：1、死荷載等穩(wěn)定因素;2、上下游的水壓力;3、地基的沉降;4、溫度;5、土和淤泥的壓力;6、冰的壓力;7、地震因素;8、風的壓力;

53、9、低于大氣壓;10、波浪的拍擊壓力11、地基的反應。</p><p>　　這樣的大壩地震安全性一直是一個嚴重問題，因為損壞的印度科依納大壩在1967年已在世界各地水壩被視為在混凝土重力壩的設計發(fā)展和地震分析的一個分水嶺事件。有關技術領域非常先進的的國家認為責任人必須執(zhí)行的政策和程序，以確保通過完善的專業(yè)實踐和大壩抗震安全是至關重要的。大壩的抗震安全關乎市民的安全因此需求更高程度的公眾信心。各種力量的估計和描述在

54、以下各節(jié)簡要提供。</p><p><b>　　2.1水壓</b></p><p>　　水壓力（P）是作用在重力壩上最主要的外部力量。水平水壓力通過存儲在大壩的上游側(cè)和下游側(cè)水的重量來施加。可從靜壓力分布的規(guī)則來估計并可以表示為</p><p><b>　?。?）</b></p><p>　　其中，

55、H是水的深度，是單位重量的水。</p><p><b>　　2.2 揚壓力</b></p><p>　　水通過空隙滲流，基礎材料的裂紋和裂縫，壩體滲水，然后通過壩體和壩基之間對大壩產(chǎn)生壓力，根據(jù)6，壩體和壩基之間的壓力強度應該等于各自的靜水壓力和直線連接的強度坐標，為了緩解排水廊道上升，廊道表面的靜水壓力應等于根部和頂部靜水壓力的1/3。</p><

56、;p><b>　　2.3 地震力</b></p><p>　　一場地震會產(chǎn)生震波，這些震波能夠以每個可能的方向震動重力壩依賴的土地。因此，一場地震帶來的影響，相當于朝當時震波傳遞的方向給壩的地基加速。</p><p>　　通常，一場地震會引起水平加速度和垂直加速度。這些加速度的值通常用重力加速度的百分比表示出來，如，a=0.10g或者0.20g，等等。一般來說，

57、加速度的值在0.10g到0.15g對地震帶的高壩通常是足夠的。在極端的地震帶，用保守的設計，甚至有時一個0.30g的值都可能被接受。</p><p>　　地震荷載（地震力）在水平和垂直方向的地震加速度應該被檢查核實。由于地震加速度可能發(fā)生在任何方向，完成時最不順的方向應該被分析考慮進去。</p><p>　　在混凝土重力壩設計中使用的地震荷載是根據(jù)設計的地震和地震評估確定的點特異性提案。根

58、據(jù)地震的嚴重程度表現(xiàn)，至少要有一個地震的評估應該對位于地震區(qū)1，2，3的所有項目來執(zhí)行，以及孟加拉國。</p><p>　　應該運用分析地震系數(shù)法來確定最終位置和滑動堤壩的穩(wěn)定性。在強地震活動的地區(qū)，動態(tài)的地震反應分析需要對內(nèi)部進行應力分析。</p><p>　　2.3.1垂直加速度的效果（av）</p><p>　　垂直加速度可能向上或者向下。當垂直加速度向上時，

59、大壩的壩基就會被抬上來，靠近大壩的壩體，這樣大壩的實際重量就會增加，因此，形成的壓力也會增加。</p><p>　　當垂直加速度向下時，大壩的壩基就會盡量向下移遠離壩體。這樣就減輕了大壩的實際重量和破壞大壩的穩(wěn)定性。因此這是對于設計來說最糟糕的了。大壩實際重量的結果可以通過下面這個公式計算出來：</p><p><b>　?。?）</b></p><

60、;p>　　在這個式子中，w是大壩的總重，kv是被用作垂直加速度的重力加速度的一部分，例如0.10或0.20等等。</p><p>　　換言之，垂直加速度減輕了壩體主堆石料和水的總重，并使其重量降到了它們原先的總重（1-kv）倍。</p><p>　　2.3.2水平加速度的效果（ah）</p><p>　　水平加速度可能導致水力壓強和水平慣性力。</p&g

61、t;<p>　　水力壓強：水平加速度朝著水庫的方向時會導致水的壓強會有瞬間的增加，因為壩基和大壩有向水庫的方向的水平加速度，而水因為慣性抵抗住了這種活動。由【9】可知，水力的大小可以通過（3）式來計算</p><p><b>　?。?）</b></p><p>　　在這個式子中Cm等于含有已知不變斜率的壓力系數(shù)的最大值，這里的Q是角度，是由大壩朝向上游的

62、一面和水平加速度形成的。Kh等于被用作水平加速度的重力加速度的一部分，例如ah=kh*g.</p><p>　　這個力在底部的瞬時作用力可以通過（4）式計算出來</p><p><b>　　（4）</b></p><p>　　水平慣性力：除了運用這種水力壓強以外，水平加速度在壩體產(chǎn)生了一種慣性力。這種慣性力的產(chǎn)生是為了保證壩體和壩基不分離。產(chǎn)生

63、的這種力的方向會和地震顯示的加速度方向相反。</p><p>　　因為一場地震可能顯示出逆流方向的加速度或者是順流方向的加速度。在大壩結構的穩(wěn)定性分析中選擇這個力的方向是不可缺少的，雖然這個方式會產(chǎn)生意料中最不想見的效果。例如，當水庫滿了，如果它和流體靜力學的水的壓強合起來，這個力就會產(chǎn)生最糟糕的結果，因此朝順流的方向運動（也就是當朝向水庫的逆流方向的地震加速度產(chǎn)生時）。當水庫是空的，如果這個力被認為是朝逆流的方