Comprehensive Evaluation On Construction And Operation Risk Of Earth-rock Dam

Earth-rock dam construction period brings many risk events, which leads to the difficulty to manage construction goals collaboratively. And potential accidents during operation period of earth rock dam pose a threat to lives and property of people who live downstream. Correct awareness and judgments to threat of different phases lay a foundation for dam design, construction and operation management, which is, however,not sufficient at present. Therefore, this study is about the research of earth-rock dam construction and operation risk evaluation with the support from the National Natural Science Foundation of China(No. 51379192) and Fund for Cultivating Outstanding Doctoral Thesis of School of Water Conservancy and Environment of Zhengzhou University. The work and results are as follows:(1) Dynamic risk factors identification of earth-rock dam during construction. Based on the Hall’s Three-dimensional Structure theory, analysis of risk formation path and construction phases, dynamic risk identification system is established from three dimensions of logic, time and knowledge by WBS-RBS matrix. Theory of logistic regression analysis is introduced which serves as the supplement for expertise experience and ranks relative importance of risk factors objectively and subjectively.(2) Dynamic overtopping risk analysis of earth-rock dam during construction. This study simulates hydrologic and hydraulic factors as well as construction schedule from Monte-Carlo simulation and establishes risk dynamic analysis model of overtopping, which reveals relevant factors uncertainty’s influence on overtopping risk, based on the analysis of key influencing factors such as upstream water, discharge of diversion structure and retaining structure’s crest level.(3) Multiple-target risk analysis of earth-rock dam during construction. An improved catastrophe theory evaluation method is proposed to solve the major problems of conventional catastrophe theory evaluation method:(a) overestimated assessment values and(b) the indistinguishability of the final values from both prior and inferior projects. In this method, an S-curved distribution is incorporated as a fitting function. The initial comprehensive evaluation value is mapped to the underlying index membership to acquire improved value of catastrophe theory evaluation method. The improved method is used to analyze multi-target risks, which include safety, quality, progress and cost during construction, and gives more objective and clear results.(4) Risk evaluation of earth-rock dam during operation. Combined with the present situation of dam safety and risk criteria in other fields, based on ALARP principles and F-N curves, risk criteria for reservoir dams in China are established which are effectively cohesive to the current safety standards. The economic, social development level and the willingness of masses to accept risk are taken into consideration, and the related parameters are pertinently demonstrated and analyzed. The criteria can evaluate the risk levels of earth-rock dam effectively under various operating conditions.