土石坝的评估和修复毕业设计外文翻译

1、附录一 外文翻译英文原文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 penetrationresistanc

33、e 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 that i

34、f 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, construct

35、ion, 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 the ci

36、vil 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 guidelin

37、es 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 slo

38、pe 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 of cy

39、clic 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.中文翻译土石坝的评估和修复待添加的隐藏文字内容3摘要：在野外实地、办公室里已进行的一系列的观察，研究，分析，使

40、本文获得了对石坝如何适应其地质环境，以及如何与水库相互影响的正确的认识。本文旨在通过对克罗顿堤坝进行的的案例分析，介绍大坝评估和修复过程中会遇到的技术难题。引言 水利或其他工程上的许多大型设备，已经非常陈旧且磨损严重；更多的业主逐渐意识到维护设施的费用在运营成本里所占的比重越来越大。因此，未来修复产业将会蓬勃发展。在土石坝建设工程上，无论是地基还是填土质量都不能在生产前达到标准或规范，并且也不能100%预测出他们的性能表现。大坝建造工程，尤其是土质结构工程，在许多方面已经取得进步并将继续改进，特别是在节约资源和可接受风险水平的测定方面更是需要改进。因此在该领域，仍存在多种改进意见和实践方法。因

41、为该领域没有公认的标准或唯一的施工程序，设计和建造大坝过程中可能会遇到一些工程建设上的问题。尽管相关技术有所进步，但是这些技术很大一部分是关于大坝建造的，而对其维护，监测和评估方面的技术都处在实验阶段。因此，如果没有统一的设计规范，很难制定出一套严格的对建成大坝的评估制度。许多机构（美国陆军工程兵团，田纳西流域管理局，联邦能源监管委员会等）已经开发出用于实地检测的核对表，例如，可行的评估报告和主题。但是这些不能被当做固定程序，只能充当指导，参考，或作为需要观察，记录之处的范例。这种核对表决不能代替一个有经验的，观察力极强的工程师。在业主同意施工后，工程师应该检测几个关键因素，这些因素相关的，结

42、合适当的静态和动态稳定性的计算结果，就形成了评估报告的基础。如果工程师熟悉并习惯于设计建造大坝，并且对该领域有足够的了解且有丰富的工程实践经验，这种评估报告则是工程师们所能提交的唯一合理的报告。修复措施 影响堤坝性能的主要因素有：(1)渗流( 2)稳定性 （3）超高。 对于一个堤坝来说，所有这些因素都是相关联的，渗流会导致腐蚀和管道渗漏，使大坝失稳。失稳则会导致坝体开裂，反过来会导致渗漏和腐蚀。为提高大坝的稳定性，防止渗漏管涌所采取的措施取决于溢出点位置（地基还是坝体），渗流量及其临界值。加高路堤边坡稳定性通常要通过填平斜坡或是加重压脚。这种斜坡加固工程通常会结合下游坡脚的排水措施。如果担心快速水位下降情况下的上流坡面的稳定性会下降，那么深入分析或监测产生的孔隙水的压力或微调水库的操作方式会消除（对于失稳）的顾虑。最后加高土坝通常是相对简单的填充操作，尤其是加高程度相对较小的填充操作更为简单。新旧填充物的接触面必须在设计和建造时被给予足够的关注以确保防水层和相关过滤器是一个连贯的整体。相对较新的材料，如防水的土工膜和加固土已被成功运用于大坝的加高工程。然而，单靠这一解决措施，大坝修复程度收效甚微。通常，需结合多种解决措施，如安装一个带减压系统的截流器。在修复工程中，维护的效果是很难预测的。通常，在修复过程中进行阶段性的监测