土石壩外文翻譯---土石壩及溢洪道設(shè)計

1、<p>　　The Design of Earth-Rock Dam and Spillways</p><p>　　Part 1 Embankment Dams</p><p>　　Selection of embankment type：</p><p>　　In general, there are two types of embankment d

2、ams: earth and rockfill. The selection 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 cha

3、racter of the rock and that no hard and fast system of classification can be made. Rocks which are soft and will easily break down under the action of excavation and placement can be classified with earthfills. Rocks whi

4、ch are hard a</p><p>　　The selection and the design of earth embankment are based upon the judgment and experience of the designer and is to a large extent of an empirical nature. The various methods of stab

5、ility and seepage analyses are used mainly to confirm the engineer’s judgment. </p><p>　　Freeboard ：</p><p>　　All earth dams must have sufficient extra height known as freeboard to prevent overt

6、opping by the pool. The freeboard must be of such height that wave action, wind setup, and earthquake effects will not result in overtopping of the dam. In addition to freeboard, an allowance must be made for settlement

7、of the embankment and the foundation which will occur upon completion of the embankment. </p><p>　　Top width ：</p><p>　　The width of the earth dam top is generally controlled by the required wid

8、th 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 massive landslides in the pool or by s

9、eismic block tipping, then extra top width of erosion resistive fill will be required.</p><p>　　Alignment ：</p><p>　　construction costs but such alignment should not be such as to encourage slid

10、ing 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 a

11、re given 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,</p><p>　　Abutments ：</p>

12、<p>　　Three problems are generally associated with the abutments of earth dams:①seepage,②instability, and ③transverse cracking of the embankment. If the abutment consists of pervious soils it may be necessary to c

13、onstruct an upstream impervious blanket and downstream drainage measures to minimize and control abutment seepage.</p><p>　　Where steep abutments exist, especially with sudden changes of slopes or with steep

14、 bluff, there exists a danger of transverse cracking of the embankment fills, This can be treated by excavation of the abutment to reduce the slope, especially in the imperious and transition zones. The transition zones,

15、 especially the upstream, should be constructed of fills which have little or no cohesion and a well-distributed gradation of soils which will promote self-healing should transverse cracking occur.</p><p>　　

16、Stage construction ：</p><p>　　It is often possible and in some cases necessary, to construct the dam embankment in stages. Factors dictating such a procedure are :①a wide valley permitting the construction o

17、f the diversion or outlet works and part of the embankment at the same time; ②a weak foundation requiring that the embankment not be built too rapidly to prevent overstressing the foundation soils;③a wet borrow area whic

18、h requires a slow cases it may construction to permit an increase in shear strength through consolidati</p><p>　　Embankment soils ：</p><p>　　Most soils are suitable for use for embankment constr

19、uction, however, there are physical and chemical limitations, soils which contain excessive salts or other soluble materials should not be used. Substantial organic content should not exist in soils. Lignite sufficiently

20、 scattered through the fill to prevent the danger of spontaneous combustion, is not objectionable. Fat clays with high liquid limits may prove difficult to work and should be avoided.</p><p>　　Compaction req

21、uirements ：</p><p>　　The strength of the impervious and semi-impervious soils depends upon he compacted densities. These depend in turn upon the water content and weight of the compacting equipment. The desi

22、gn 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

23、the natural water content is too high, then it may be reduced in borrow area by drainage, or b</p><p>　　If necessary, test fills should be constructed with variations in placement water content, lift thickne

24、ss, number of roller passes and type of rollers. For cases of steep abutment, the fill must be placed in thin lifts and compacted by mechanical hand tampers. All overhangs should either be removed or filled with lean con

25、crete prior to fill placement.</p><p>　　Types of instruments ：</p><p>　　The type of instrumentation depends upon the size and complexity of the project. The devices in common use are :①piezomete

26、rs; ②surface movements; ③settlement gages; ④inclinometers; ⑤internal movement and strain indicators; ⑥pressure cells; ⑦movement indicators at conduit joints and other concrete structures.</p><p>　　Part 2 Spi

27、llways</p><p>　　A spillway is the safety valve for a dam. It must be designed to discharge maximum flow while keeping the reservoir below a predetermined level. A safe spillway is extremely important. Many f

28、ailures of dams have resulted from improperly designed spillways or spillways of insufficient capacity. Spillway size and frequency of use depend on the runoff characteristics of the drainage basin and the nature of the

29、project. The determination and selection of the reservoir inflow design flood must be bas</p><p>　　Space limitations do not permit an adequate hydrologic treatment of flood flows. However, data are supplied

30、for estimates of maximum flows for the initial project studies. A more detailed hydrologic analysis is necessary for the utilization of the annual and long-turn stream flow in a proper project formulation.</p><

31、;p>　　The study of stream or river flows involves:①the determination of the amount of water available throughout a period of years；and ②the determination of the maximum volumes of water that must be handled for spillwa

32、y design and dam safety.</p><p>　　In the first aspect, the flow is studied for periods of drought and programmed into this study. A mass curve of the stream runoff over a period of years is developed to dete

33、rmine the available water. The mass curve is the accumulative total of the volume of flow past a given point on the stream over a period of time. Unfortunately, most of the small streams do not have sufficient records to

34、 develop the hydrologic information. The engineer usually develops synthetic curves from neighboring stream</p><p>　　The second aspect involves estimating maximum flood flow to determine spillway requirement

35、 and dam safety. Studies show that flood flows are associated with frequency of the event of the risk of floods causing damage by exceeding the estimated design flow.</p><p>　　If failure of the dam would res

36、ult in loss of life, the spillway must have sufficient capacity to prevent failure when the maximum probable flood is routed through the reservoir. This is particularly important in rock and earthfill dam that may be ove

37、rtopped during a flood. Concrete dams can generally withstand some overtopping without failure if the structural analysis adheres to the generally accepted safety factors.</p><p>　　The case of dam failure th

38、at does not endanger life may be justified if the organization involved fully realizes the risks and ensuing damages. This situation may exist on low, small reservoir-type dams.</p><p>　　A quick estimates of

39、 maximum probable flow can be obtained from a figure. Discharge determined from these curves should be modified by application of hydrologic data pertinent to the area. The curves are based records of unusual flood disch

40、arges for unregulated streams. </p><p>　　The engineer should not accept the flood peak established from these experience curves without first bringing the data up to date to show all recent flood events and

41、those pertinent to the area of study. </p><p>　　An advanced procedure to estimate the maximum flood is to transpose storm producing great floods in the region over the drainage basin. The resulting flood is

42、analyzed to determine the peak flow and the hydrograph. The hydrograph is the relationship of discharge and time for precipitation when combined with other flood-contributing of the basin (including melting snow)to produ

43、ce the flood hydrograph.</p><p>　　Flood less than maximum may be used for structures where loss of human life is not involved. In minor structures with insignificant storage, where it is permissible to antic

44、ipate failure within the useful life of the project, a 50-year or 100-year frequency flood may be used for the inflow design flood.</p><p>　　Site conditions greatly influence the location, type, and componen

45、ts of the spillway. The type of dam construction is also influenced by the type of spillway and spillway requirements.</p><p>　　There are six general categories of spillways: ①overflow ,②through or chute, ③s

46、ide channel, ④shaft or glory hole, ⑤siphon, ⑥gated. The designer may use one or a combination of types to fulfill the project needs.</p><p>　　Some designs will use one type of spillway for normal operation a

47、nd for flood peaks up to a 50-year or 100-year frequency storm. An emergency spillway provides additional safety if emergencies arise that was not covered by normal design assumptions. Such situations could result from f

48、loods 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</

49、p><p>　　The overflow spillway is well suited to concrete dams. It is commonly used where dams have sufficient crest length for the desired discharge capacity and where the foundation material is solid or can be

50、 protected against scouring. Some dams use a free overflow or non-supported type; others incorporate a chute or through to carry the flow to the downstream channel.</p><p>　　Chute spillways are often used fo

51、r earth dams or where there are poor downstream foundation materials. Slide channels and shaft spillways are readily adapted to narrow canyons where space is limited. Limitations on crest length or maintaining a constant

52、 headwater level fit the flow characteristics of a siphon spillway. Gated spillways are used when it is desirable to limit the effects of the dam during high flows and prevent excessive flooding.</p><p>　　Th

53、e spillway may be part of the dam or a separate structure. Its function must be integrated with the dam. The location, size, and other dam features influence the spillway location and arrangement. The final plan is gover

54、ned by the overall economy and hydraulic sufficiency of the spillway.</p><p>　　───This literature is from《Hydraulic Engineering Specialty English》</p><p><b>　　土石壩及溢洪道設(shè)計</b></p>

55、<p><b>　　1 土石壩的設(shè)計</b></p><p>　　壩型的選擇：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處取得合用材料的情況。應(yīng)該注意，根據(jù)巖石的物理性質(zhì)，堆石能逐漸變化為填土，因而不能對堆石作出嚴格而固定的分類。那些脆弱和在開挖填筑時容易破裂的巖石可歸入填土類。而堅硬和不易破裂的巖石則列入堆石類。</p>

56、;<p>　　一座土壩的選定和設(shè)計都有賴于設(shè)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。</p><p>　　超高的確定：所有的土石壩都必須有一個足夠的額外高度，成為超高，以防止庫水漫頂。超高的高度必須足以在波浪作用、風力雍高和地震影響下，不會導(dǎo)致壩的漫頂。除了超高外，對于壩建成時發(fā)生的壩體和地基沉陷，還必須在高度上留有余地。<

57、;/p><p>　　壩頂寬度：土壩的壩頂寬度一般采用常規(guī)設(shè)備便于填筑的寬度來控制。通常，把頂寬度應(yīng)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寬度。</p><p>　　定線：土壩的壩軸線選定應(yīng)盡量使建設(shè)費用降到最少，但是也不能因此而引起壩體發(fā)生滑動或開裂。一般說來，一條橫跨河谷的最短直線，可能滿足要求。但是當?shù)?/p>

58、的地形和地基條件可能要求采用另外的方案。位于峽谷的壩，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，能使壩體壓緊，從而盡量減小其橫向開裂。</p><p>　　兩岸壩座：一般有三個問題與土壩壩座有關(guān)：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(gòu)成，就可能建造一道與上游不透水鋪蓋和下游排水設(shè)施，以盡量減少和控制壩座內(nèi)的滲透。</p><p>　　在壩座岸坡很陡的

59、地方，特別在邊坡突變或有陡壁處，那里的壩體填土?xí)挟a(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)生橫向裂縫時可自行愈合。</p><p>　　分期施工：土壩的分期施工往往是可能的，而且在一些情況下是必須的。要求這樣施工程序的因素是：①河谷寬闊，可以允許導(dǎo)流或泄水工程于一

60、些部分壩體同時施工；②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(yīng)力；③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(shè)基礎(chǔ)排水設(shè)施或填筑排水砂井，或采用水平透水的排水鋪蓋。</p><p>　　壩體的土料：大多數(shù)土料適用于壩體填筑。然而，在物理和化學(xué)性質(zhì)上也有一定的限制。含有過多鹽分獲可溶性物質(zhì)的土料，不可使用。在土料里，不應(yīng)存在大量的有機質(zhì)成分。褐煤若能通過

61、填筑而充分分散，無自然之虞，就不能妨礙使用。而具有高度流限的肥粘土，多半難以施工，必須避免使用。</p><p>　　壓實的要求：不透水和半透水的土料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(shè)備的質(zhì)量。因此，料場土料的含水量和在堆筑前或堆筑后而未碾壓前的填土實際含水量變化，都會影響壩體的設(shè)計。若果天然含水量太高，可以在料場用排水或?qū)⑼亮习宜傻霓k法來減低。如果土料太干燥，則須在料場用灑水或泡水的辦法

62、把土料潤濕，然后再讓涂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。透水性土料應(yīng)壓實到相對密度的80%。</p><p>　　如果需要，應(yīng)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(yīng)在填土填筑以前挖除或用貧混凝土填平。</p><

63、p>　　觀測儀器的類型：觀測儀器的類型取決于工程的規(guī)?；驈?fù)雜性。通常的裝置是：①測壓計；②表面位移標志；③沉陷量觀測儀；④測斜儀；⑤內(nèi)部位移和應(yīng)變指示儀；⑥壓力盒（壓力傳感器或壓應(yīng)力計）；⑦地震加速儀；⑧在管道接頭和其他混凝土結(jié)構(gòu)上的位移標志。</p><p><b>　　2溢洪道</b></p><p>　　溢洪道相當于壩上的一個安全閥，它必須設(shè)計成能夠泄放最

64、大的流量，而同時能保持水庫的水位在預(yù)定的水位以下。一個安全的溢洪道是極為重要的，許多壩的失事都是由溢洪道設(shè)計不當或者溢洪道容量不足造成的。溢洪道的尺寸和使用頻率取決于流域的徑流特性和工程的性質(zhì)。入庫設(shè)計洪水的選擇和確定，則必須在充分研究流域水文因素的基礎(chǔ)上進行。對于過壩流水的調(diào)泄，需要有合理審慎的設(shè)計，以避免生命財產(chǎn)的損失。</p><p>　　由于篇幅限制，這里不允許對洪水流量的水文分析做充分的討論。但是提供了

65、作工程初步研究的最大流量估算資料。至于在工程的正式規(guī)劃中隊河川水流作年或多年利用時，則需要進行更詳細的水文分析。</p><p>　　對江河流量的研究包括：確定經(jīng)若干年一段時期內(nèi)所能獲得的水量；確定溢洪道的設(shè)計和大壩安全所必須宣泄的最大水量。</p><p>　　第一方面，要聯(lián)系工程開發(fā)中的用水情況，按枯水期和豐水期來研究流量。優(yōu)先的用水權(quán)必須調(diào)查清楚，并納入研究中，要做出若干年一段時期內(nèi)

66、河川徑流的累積曲線，以便確定可利用的水量。累積曲線表示一定時期內(nèi)通過河道上某一地點的累積總量。遺憾的是，大部分小河流上都沒有足夠的記錄可以用以編制水文資料。工程技術(shù)人員通常都從相鄰的河流數(shù)據(jù)和雨量資料編制出綜合曲線。從各種教材、雜志和報告中也可以得到各種估算河流流量的方法。</p><p>　　第二方面包括最大洪水流量的估算，用以確定所需要的溢洪道容量和壩的安全。研究表明，洪水流量與不同時期中洪水的出現(xiàn)頻率有關(guān)。

67、這樣，工程技術(shù)人員就能切實地估計洪水超過估算的設(shè)計流量所造成損失的危害性。</p><p>　　如果壩的失事會造成生命傷亡，則溢洪道必須有充分的容量，以防止最大可能洪水通過水庫是發(fā)生失事。這種情況對于發(fā)生洪水時可能漫頂?shù)耐翂魏投咽瘔危葹橹匾?，混凝土壩如果在結(jié)構(gòu)分析中遵守通用的安全系數(shù)，通常都能夠經(jīng)受一定程度的漫頂而不致失事。</p><p>　　對于不致危及生命的失事情況，如果有關(guān)部門充

68、分估計到所冒的風險以及隨之而造成的損失，則也是允許的。這種情況可能存在于小水庫的低壩上。</p><p>　　用查圖法可以快速估算出最大可能流量。由這些曲線定出的流量，應(yīng)采用與該地區(qū)有關(guān)的水文資料加以修正。這些曲線系根據(jù)未經(jīng)整治的河流的非常洪水流量記錄作出的。</p><p>　　工程技術(shù)人員首先要取得列有全部近期洪水過程的資料，以及與研究地區(qū)有關(guān)的資料，然后才能采用從這些經(jīng)驗曲線上得出的

69、洪峰流量。估算最大洪水的一種先進方法是將地區(qū)內(nèi)能產(chǎn)生大洪水的暴雨轉(zhuǎn)換成流域的洪水，將所得出的洪水加以分析，就可以用來確定洪峰流量和流量過程線。流量過程線是表示洪水產(chǎn)生特性的流量—時間關(guān)系曲線。如果用綜合流域內(nèi)的其他洪水形成特性（包括融雪）來研究最大可能降水量，則也可以得到相似的方法求出洪水過程線。</p><p>　　對于失事不會導(dǎo)致人員傷亡的的建筑物，也可以采用比最大流量洪水的洪水值。在蓄水量不多的較小結(jié)構(gòu)上，

70、容許在工程使用年限內(nèi)發(fā)生預(yù)期的失事時，入庫設(shè)計洪水可以采用50年或100年一遇的頻率。</p><p>　　壩址條件對于溢洪道的位置、型式和組成部分有很大影響。而溢洪道的型式和對泄洪的各種要求對壩的構(gòu)造型式也有影響。</p><p>　　溢洪道有六種常用類型：頂部溢流式；陡槽式；側(cè)槽式；豎井或喇叭式；虹吸式；閥門式。設(shè)計人員可以采用一種或幾種型式的組合以滿足工程的要求。</p>

71、<p>　　有些設(shè)計中，采用一個型式溢洪道供正常運行用，應(yīng)付50年或100年一遇暴雨的洪峰。另一個非常溢洪道，則在發(fā)生正常設(shè)計假定沒有考慮的非常情況時，提供附加安全度。這類情況可以發(fā)生在洪水超過某一水位、溢洪道閥門發(fā)生故障或泄水道強制關(guān)閉時。非常溢洪道能防止壩的重要部位漫頂，對于土壩和堆石壩就顯得特別需要。</p><p>　　頂部溢流式洪道適合于混凝土壩，常用在那些壩頂長度可以滿足所需泄洪容量的地

72、方和壩基堅固或能抗沖刷得地方。有些壩上采用自由溢流式，令一些壩上則設(shè)置陡槽將水泄入下游河道。</p><p>　　陡槽式溢洪道常在土壩或下游地基材料不良的地方。側(cè)槽和豎井溢洪道則多用于空間受到限制的峽谷中。虹吸式溢洪道的水流特性適用于壩頂長度有限或要保持固定庫水位的地方。當希望在大流量時減少壩的阻止影響和防止淹沒過多時，都采用有閥門的溢洪道。</p><p>　　溢洪道可以是壩的一部分，也