土石壩的評估和修復(fù)畢業(yè)設(shè)計外文翻譯

1、附錄一 外文翻譯英文原文assessment and rehabilitation of embankment damsnasim uddin, p.e., m.asce1abstract: a series of observations, studies, and analyses to be made in the field and in the office are presented to gain a proper understanding of how an embankment dam fits into its geologic setting and how it in

2、teracts with the presence of the reservoir it impounds. it is intended to provide an introduction to the engineering challenges of assessment and rehabilitation of embankments, with particular reference to a croton dam embankment.doi: 10.1061/(asce)0887-3828(2002)16:4(176)ce database keywords: rehab

3、ilitation; dams, embankment; assessment.introduction many major facilities, hydraulic or otherwise, have become very old and badly deteriorated; more and more owners are coming to realize that the cost of restoring their facilities is taking up a significant fraction of their operating budgets. reha

4、bilitation is, therefore, becoming a major growth industry for the future. in embankment dam engineering, neither the foundation nor the fills are premanufactured to standards or codes, and their performance correspondingly is never 100% predictable. dam engineeringin particular, that related to ear

5、th structureshas evolved on many fronts and continues to do so, particularly in the context of the economical use of resources and the determination of acceptable levels of risk. because of this, therefore, there remains a wide variety of opinion and practice among engineers working in the field. ma

6、ny aspects of designing and constructing dams will probably always fall within that group of engineering problems for which there are no universally accepted or uniquely correct procedures.in spite of advances in related technologies, however, it is likely that the building of embankments and theref

7、ore their maintenance, monitoring, and assessment will remain an empirical process. it is, therefore, difficult to conceive of a set of rigorousassessment procedures for existing dams, if there are no design codes. many agencies (the u.s. army corps of engineers, usbr, tennessee valley authority, fe

8、rc, etc.) have developed checklists for field inspections, for example, and suggested formats and topics for assessment reporting. however, these cannot be taken as procedures; they serve as guidelines, reminders, and examples of what to look for and report on, but they serve as no substitute for an

9、 experienced, interested, and observant engineering eye. several key factors should be examined by the engineer in the context of the mandate agreed upon with the dam owner, and these together with relevant and appropriate computations of static and dynamic stability form the basis of the assessment

10、. it is only sensible for an engineer to commit to the evaluation of the condition of, or the assessment of, an existing and operating dam if he/she is familiar and comfortable with the design and construction of such things and furthermore has demonstrated his/her understanding and experience. reha

11、bilitation measures the main factors affecting the performance of an embankment dam are (1)seepage; (2)stability; and (3) freeboard. for an embankment dam, all of these factors are interrelated. seepage may cause erosion and piping, which may lead to instability. instability may cause cracking, whic

12、h, in turn, may cause piping and erosion failures. the measures taken to improve the stability of an existing dam against seepage and piping will depend on the location of the seepage (foundation or embankment), the seepage volume, and its criticality. embankment slope stability is usually improved

13、by attening the slopes or providing a toe berm. this slope stabilization is usually combined with drainage measures at the downstream toe. if the stability of the upstream slope under rapid drawdown conditions is of concern, then further analysis and/or monitoring of resulting pore pressures or modi

14、cations of reservoir operationsmay eliminate or reduce these concerns. finally, raising an earth ll dam is usually a relatively straightforward ll placement operation, especially if the extent of the raising is relatively small. the interface between the old and new lls must be given close attention

15、 both in design and construction to ensure the continuity of the impervious element and associated filters. relatively new materials, such as the impervious geomembranes and reinforced earth, have been used with success in raising embankment dams. rehabilitation of an embankment dam, however, is rar

16、elyachieved by a single measure. usually a combination of measures, such as the installation of a cutoff plus a pressure relief system, is used. in rehabilitation work, the effectiveness of the repairs is difficult to predict; often, a phased approach to the work is necessary, with monitoring and in

17、strumentation evaluated as the work proceeds. in the rehabilitation of dams, the security of the existing dam must be an overriding concern. it is not uncommon for the dam to have suffered significant distressoften due to the deficiencies that the rehabilitation measures are to address.the dam may b

18、e in poor condition at the outset and may possibly be in a marginally stable condition. therefore, how the rehabilitation work may change the present conditions, both during construction and in the long term, must be assessed, to ensure that it does not adversely affect the safety of the dam. in the

19、 following text, a case study is presented as an introduction to the engineering challenges of embankment rehabilitation, with particular reference to the croton dam project.case study the croton dam project is located on the muskegon river in michigan. the project is owned and operated by the consu

20、mer power company. the project structures include two earth embankments, a gated spillway, and a concrete and masonry powerhouse. the earth embankments of this project were constructed of sand with concrete core walls. the embankments were built using a modified hydraulic fill method. this method co

21、nsisted of dumping the sand and then sluicing the sand into the desired location. croton dam is classified as a high-hazard dam and is in earthquake zone 1. as part of the ferc part 12 inspection (ferc 1993), an evaluation of the seismic stability was performed for the downstream slope of the left e

22、mbankment at croton dam. the croton dam embankment was analyzed in the following manner. soil parameters were chosen based on standard penetration (n) values and laboratory tests, and a seismic study was carried out to obtain the design earthquake. using the chosen soil properties, a static finite-e

23、lement study was conducted to evaluate the existing state of stress in the embankment. then a one-dimensional dynamic analysis was conducted to determine the stress induced bythe design earthquake shaking. the available strength was compared with expected maximum earthquake conditions so that the st

24、ability of the embankment during and immediately after an earthquake could be evaluated. the evaluation showed that theembankment had a strong potential to liquefy and fail during the design earthquake. the minimum soil strength required to eliminate the liquefaction potential was then determined, a

25、nd a recommendation was made to strengthen the embankment soils by insitu densification. seismic evaluation two modes of failure were considered in the analysesnamely, loss of stability and excessive deformations of the embankment. the following analyses were carried out in succession: (1) determina

26、tion of pore water pressure buildup immediately following the design earthquake; (2) estimation of strength for the loose foundation layer during and immediately following the earthquake; (3) analysis of the loss of stability for postearthquake loading where the loose sand layer in the embankment is

27、 completely liquefied; and (4) liquefaction impact analysis for the loose sand layer for which the factor of safety against liquefaction is unsatisfactory.liquefaction impact assessment based on the average of the corrected spt value and cyclic stress ratio (tokimatsu and seed 1987), a total settlem

28、ent of the 4.6 m(15 ft) thick loose embankment layer due to complete liquefaction was found to be 0.23 m (0.75 ft).permanent deformation analysis based on a procedure by makdisi and seed (1977), permanent deformation can be calculated using the yield acceleration, and the time history of the average

29、d induced acceleration. since the factor of safety against flow failure immediately following theearthquake falls well short of that required by ferc, the newmark type deformation analysis is unnecessary. therefore, it can be concluded that the embankment will undergo significant permanent deformati

30、on following the earthquake, due to slope failure in excess of the liquefaction-induced settlement of 0.23 m (0.75ft).embankment remediation based on the foregoing results, it was recommended to strengthen the embankment by in situ densification. an analysis was carried out to determine the minimum

31、soil strength required to eliminate the liquefaction potential. the analysis was divided into three parts, as follows. first, a slope stability analysis using the computer program pcstabl (purdue 1988)# of the downstream slope of the left embankment was conducted. strength and geometric parameters w

32、ere varied in order to determine the minimum residual shear strength and minimum zone of soil strengthening required for a postearthquake stability factor of safety, (fs)>1.second, spt corrections were made. the minimum residual shear strength correlates to a corrected/normalized penetrationresis

33、tance value (n1) of 60. from this value, a backcalculation was performed to determine the minimum field measure standard penetration resistance n values (blows per foot). third, liquefaction potential was reevaluated based on the minimum zone of strengthening and minimum strength in order to show th

34、at if the embankment is strengthened to the minimum value, then the liquefaction potential in the downstream slope of the left embankment will, for all practical purposes, be eliminated.conclusion key factors to be considered in dam assessment and rehabilitation are the completeness of design, const

35、ruction, maintenance and monitoring records, and the experience, background, and competence of the assessing engineer. the paper presents a recently completed project to show that the economic realization of thistype of rehabilitation inevitably rests to a significant degree upon the expertise of th

36、e civil engineers.referencesduncan, j. m., seed, r. b., wong, k. s., and ozawa, u. (1984). feadam: a computer program for finite element analysis of dams. geotechnical engineering research rep. no. su/gt/84-03,dept. of civil engineering, stanford univ., stanford, calif.ferc. (1993). engineering guid

37、elines for the evaluation of hydropower projects. 0119-2.makdisi, f. i., and seed, h. b. (1977). a simplified procedure forestimatingearthquake induced deformations in dams and embankments. rep. no. eerc 77-19, univ. of california, berkeley, calif.purdue univ. (1988). pcstabl: a computer program for

38、 slope stability analysis. rep., west lafayette, ind.schnabel, p. b., lysmer, j, and seed, h. b. (1972). shake: a computer program for earthquake response analysis of horizontally layered site. rep. no. eerc 72-12, univ. of california, berkeley, calif.seed and harder. (1990). an spt-based analysis o

39、f cyclic pore pressure generation and undrained residual strength. proc., h. bolton seed memorial symp., 2, 351376.tokimatsu, k., and seed, h. b. (1987). evaluation of settlements of sands due to earthquake shaking. j. geotech. eng., 113(8), 861878.中文翻譯土石壩的評估和修復(fù)摘要：在野外實地、辦公室里已進行的一系列的觀察，研究，分析，使本文獲得了對石

40、壩如何適應(yīng)其地質(zhì)環(huán)境，以及如何與水庫相互影響的正確的認識。本文旨在通過對克羅頓堤壩進行的的案例分析，介紹大壩評估和修復(fù)過程中會遇到的技術(shù)難題。引言 水利或其他工程上的許多大型設(shè)備，已經(jīng)非常陳舊且磨損嚴重；更多的業(yè)主逐漸意識到維護設(shè)施的費用在運營成本里所占的比重越來越大。因此，未來修復(fù)產(chǎn)業(yè)將會蓬勃發(fā)展。在土石壩建設(shè)工程上，無論是地基還是填土質(zhì)量都不能在生產(chǎn)前達到標準或規(guī)范，并且也不能100%預(yù)測出他們的性能表現(xiàn)。大壩建造工程，尤其是土質(zhì)結(jié)構(gòu)工程，在許多方面已經(jīng)取得進步并將繼續(xù)改進，特別是在節(jié)約資源和可接受風(fēng)險水平的測定方面更是需要改進。因此在該領(lǐng)域，仍存在多種改進意見和實踐方法。因為該領(lǐng)域沒有公

41、認的標準或唯一的施工程序，設(shè)計和建造大壩過程中可能會遇到一些工程建設(shè)上的問題。盡管相關(guān)技術(shù)有所進步，但是這些技術(shù)很大一部分是關(guān)于大壩建造的，而對其維護，監(jiān)測和評估方面的技術(shù)都處在實驗階段。因此，如果沒有統(tǒng)一的設(shè)計規(guī)范，很難制定出一套嚴格的對建成大壩的評估制度。許多機構(gòu)（美國陸軍工程兵團，田納西流域管理局，聯(lián)邦能源監(jiān)管委員會等）已經(jīng)開發(fā)出用于實地檢測的核對表，例如，可行的評估報告和主題。但是這些不能被當做固定程序，只能充當指導(dǎo)，參考，或作為需要觀察，記錄之處的范例。這種核對表決不能代替一個有經(jīng)驗的，觀察力極強的工程師。在業(yè)主同意施工后，工程師應(yīng)該檢測幾個關(guān)鍵因素，這些因素相關(guān)的，結(jié)合適當?shù)撵o態(tài)和

42、動態(tài)穩(wěn)定性的計算結(jié)果，就形成了評估報告的基礎(chǔ)。如果工程師熟悉并習(xí)慣于設(shè)計建造大壩，并且對該領(lǐng)域有足夠的了解且有豐富的工程實踐經(jīng)驗，這種評估報告則是工程師們所能提交的唯一合理的報告。修復(fù)措施 影響堤壩性能的主要因素有：(1)滲流( 2)穩(wěn)定性 （3）超高。 對于一個堤壩來說，所有這些因素都是相關(guān)聯(lián)的，滲流會導(dǎo)致腐蝕和管道滲漏，使大壩失穩(wěn)。失穩(wěn)則會導(dǎo)致壩體開裂，反過來會導(dǎo)致滲漏和腐蝕。為提高大壩的穩(wěn)定性，防止?jié)B漏管涌所采取的措施取決于溢出點位置（地基還是壩體），滲流量及其臨界值。加高路堤邊坡穩(wěn)定性通常要通過填平斜坡或是加重壓腳。這種斜坡加固工程通常會結(jié)合下游坡腳的排水措施。如果擔(dān)心快速水位下降情況下的上流坡面的穩(wěn)定性會下降，那么深入分析或監(jiān)測產(chǎn)生的孔隙水的壓力或微調(diào)水庫的操作方式會消除（對于失穩(wěn)）的顧慮。最后加高土壩通常是相對簡單的填充操作，尤其是加高程度相對較小的填充操作更為簡單。新舊填充物的接觸面必須在設(shè)計和建造時被給予足夠的關(guān)注以確保防水層和相關(guān)過濾器是一個連貫的整體。相對較新的材料，如防水的土工膜和加固土已被成功運用于大壩的加高工程。然而，單靠這一解決措施，大壩修復(fù)程度收效甚微。通常，需結(jié)合多種解決措施，如安裝一個帶減壓系統(tǒng)的截流器。在修復(fù)工程中，維護的效果是很難預(yù)測的。通常，在修復(fù)過程中進行階段性的監(jiān)測和