1、 中文 2575 字 附录一 外文翻译 英文原文 Assessment and Rehabilitation of Embankment Dams Nasim Uddin, P.E., M.ASCE1 Abstract: 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 settin
2、g and how it interacts 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 Databas
3、e keywords: Rehabilitation； 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 opera
4、ting budgets. Rehabilitation 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, t
5、hat related to earth 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 workin
6、g in the field. Many 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 emb
7、ankments and therefore their maintenance, monitoring, and assessment will remain an empirical process. It is, therefore, difficult to conceive of a set of rigorous assessment procedures for existing dams, if there are no design codes. Many agencies (the U.S. Army Corps of Engineers, USBR, Tennessee
8、Valley Authority, FERC, 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
9、no substitute for an 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 bas
10、is of the assessment. 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
11、and experience. Rehabilitation 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
12、cause cracking, which, 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
13、is usually improved 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 po
14、re pressures or modications of reservoir operations may 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
15、given close attention 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
16、 dam, however, is rarely achieved 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,
17、with monitoring and instrumentation 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.
