Research On Earth Dam Overtopping And Instability Fuzzy Risk Analysis

This paper introduces comprehensively the basic theory and calculation methods of risk analysis. In view of the absence of fuzziness analysis in the traditional risk analysis, fuzzy risk analysis, which, together with randomness, constitutes the two inseparable uncertainty elements, deserves exposition. Based on the theory of risk analysis and fuzzy mathematics, three calculation models of fuzzy risk are established and solution is presented. This solution transforms fuzzy variables into random variables by level cut set so that fuzzy risk can be calculated with traditional risk calculation methods.In view of the great number of earth dams, the high proportion of dam failure in China, and overtopping and instability are the two main causes to dam failure, this paper puts emphasis on the calculation of earth dam overtopping and instability fuzzy risk. After having analyzed the fuzziness and randomness of all factors, the overtopping and instability fuzzy risk models of earth dam are established. The paper approaches the inapplicability of analysis method to the two above-mentioned mathematical models by using dispersed demoted numerical virtue method. Programs are worked out and used for calculating overtopping and instability fuzzy risk of the Cheng Bi He Reservoir.The result shows that it is practicable to analyze the fuzzy risk of earth dam. With fuzziness considered, risk falls into circumscription category, and it is more reasonable and in more accordance with actual engineering compared with the traditional risk determinative value. Because the fuzzy risk standard of dam failure has not been established, the traditional risk standard is used for the safety evaluation in this paper.