UNIT 5Spillway

1、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 failures of dams have resulted from improperly designed spillways or spillways of insufficient capacity.溢洪道相當(dāng)于

2、壩上的一個安全閥，它必須設(shè)計成能夠泄放最大的流量，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(dāng)或者溢洪道容量（泄量）不足造成的。Spillway size and frequency of use depend on the runoff characteristics of the drainage basin and the nature of the project. The determination and selection of the reservoir inflow design flood must be based

3、 on an adequate study of the hydrologic factors of the basin. The routing of the flow past the dam requires a reasonably conservative design to avoid loss of life and property damage.溢洪道的尺寸和使用頻率取決于流域特性和工程性質(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。對于過壩水流的調(diào)泄，需要有合理謹(jǐn)慎的設(shè)計，以避免生命和財產(chǎn)的損失。Space limitations do not p

4、ermit an adequate hydrologic treatment of flood flows. However, data are supplied 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-term stream flow in a proper project formulation. 由于篇幅限制，這里不允許

5、對洪水流量的水文分析做充分的討論。但是提供了做工程初步研究用的最大流量估算資料。至于在工程的正式規(guī)劃中對河床水流作年或多年利用時，則需要進行更詳細(xì)的水文分析。The study of stream or river flows involves: the determination of the amount of water available throughout a period of years; and the determination of the maximum volumes of water that must be handled for spillway design

6、and dam safety.對江河流量的研究包括：確定經(jīng)若干年一段時間內(nèi)所能獲得的水量；確定溢洪道設(shè)計和大壩安全所必須宣泄的最大水量。In the first aspect, the flow is studied for periods of drought and periods of excess water in relation to use in the project development. Prior water rights must be investigated and programmed into this study. A mass curve of the s

7、tream runoff over a period of years is developed to determine the available water.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)查清除，并納入研究中。要做出若干年一段時期內(nèi)河川徑流的累積曲線，以便確定可利用的水量。 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

8、, most of the small streams do not have sufficient records to develop the hydrologic information. 遺憾的是，大部分小河流上都沒有足夠的記錄可用以編制水文資料。 The engineer usually develops synthetic curves from neighboring stream data and rainfall information. However, methods are available in various texts, journals, and report

9、s to estimate stream flow.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川流量的方法。The second aspect involves estimating maximum flood flow to determine spillway requirement and dam safety. Studies show that flood flows are associated with frequency of the event occurring within different time per

10、iods. This permits the engineer to make a realistic estimate of the risk of floods causing damage by exceeding the estimated design flow.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度。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)。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。If failure of the dam would result in loss of life, the spillway

11、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 overtopped during a flood. 如果壩的失事會造成生命傷亡，則溢洪道必須有充足的容量，以防止最大可能洪水通過水庫時發(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?，尤為重要。Concrete dams ca

12、n generally withstand some overtopping without failure if the structural analysis adheres to the generally accepted safety factors.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)售一定程度的漫頂而不致失事。The case of dam failure that does not endanger life may be justified if the organization involved fully realizes the risks and

13、ensuring damages. This situation may exist on low, small reservoir-type dams.對于不致危及生命的失事情況，如果有關(guān)部門充分估算到所冒的風(fēng)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。A quick estimate of maximum probable flow can be obtained from a figure. Discharge determined from these curves should be modified by application of hydrologi

14、c data pertinent to the area. 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。The curves are based on records of unusual flood discharges for unregulated streams. Creager gives the equation for the envelope curve in the general form as這些曲線系根據(jù)未經(jīng)整治的河流上的非常洪水流量記錄做出的。克里格（Creager）給出包絡(luò)線的一般公式為：Which: is est

15、imated maximum flood peak, cf3/s ; is corresponding flood expressed in cfs per square mile of drainage area; is drainage basin area in square miles; is coefficient depending on characteristics of drainage area.式中： 為估算的最大洪峰流量，英尺3/秒； 為相應(yīng)洪水流量，以每平方英里流域面積上立方英尺每秒計； 為流域面積；為流域面積特性系數(shù)。The engineer should not

16、accept the flood peak established from these experience curves without first bringing the data up to date to show all flood events and those pertinent to the area of study. The coefficient of generally provides a conservative estimate of flood potential for initial design layout.工程技術(shù)人員首先要取得列有全部近期洪水過

17、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)驗曲線上得出的洪峰流量。在初設(shè)布置中取系數(shù) ，通?？梢缘玫狡诎踩暮樗赡苤?。An advanced procedure to estimate the maximum flood is to transpose storms producing great floods in the region over the drainage basin. The resulting flood is analyzed to determine the peak flow and the flow hydrograph. The hydrogr

18、aph is the relationship of discharge and time for flood-producing characteristics. 估算最大洪水的一種先進方法是將該地區(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。 A similar approach results from studying the maximum probable precipitation when combined with other flood-contributing char

19、acteristics of the basin (including melting snow) to produce the flood hydrograph.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。Floods 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

20、 to anticipate failure within the useful life of the project, a 50-year or 100-year frequency flood may be used for the inflow design flood.對于失事不會導(dǎo)致人員傷亡的建筑物，也可以采用比最大洪水小的洪水值。在蓄水量不多的較小結(jié)構(gòu)上，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。Site conditions greatly influence the location, type, and components of

21、 the spillway. The type of dam construction is also influenced by the type of spillway and spillway requirements.壩址條件對于溢洪道的位置、型式和組成部分有很大的影響。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。There are six general categories of spillways： Overflow, trough or chute, side channel, shaft or glory hole,siphon, gated. The desig

22、ner may use one or a combination of types to fulfill the project needs.溢洪道有六種常用類型：頂部溢流式；陡槽式；側(cè)槽式；豎井式或喇叭口式；虹吸式 ；閘門式。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。Some designs will use one type of spillway for normal operation and for flood peaks up to a 50-year or 100-year frequency storm. 有些設(shè)計中，采用一種型式溢洪道供正常運行用，應(yīng)付50年或10

23、0年一遇的洪峰。An emergency spillway provides additional safety if emergencies arise that was not covered by normal design assumptions, such situations could result from floods above a certain level, malfunctioning spillway gates, or enforced shutdown of outlet works.另一個非常溢洪道，則在發(fā)生正常設(shè)計假定中沒有考慮的非常情況時，提供附加安全度。

24、這類情況可以發(fā)生在洪水超過某一水位、溢洪道閘門發(fā)生故障或泄水道強制關(guān)閉時。 The emergency spillway prevents overtopping the main portion of the dam and is particularly needed for earth and rock embankments.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。The overflow spillway is well suited to concrete dams. It is commonly used where dams have sufficie

25、nt crest length for the desired discharge capacity and where the foundation material is solid or can be protected against scouring. Some dams use a free overflow or non-supported type; others incorporate a chute or trough to carry the flow to the downstream channel.頂部溢流式溢洪道很適合于混凝土壩，常用在那些壩頂長度可以滿足所需泄流容量的地方和壩基堅固或能抗沖刷的地方。有些壩上采用自由溢流式，另一些壩上則設(shè)置陡槽將水泄入下游河道。Chute spillways are often used for earth dams or where there are poor downstream foundation materials. Side channels and shaf