土坝漫坝模糊风险分析

Analysis of overflow fuzzy risk on earth dam

对土坝枢纽的事故风险进行识别、对各种失事形式的影响因素的不确定性 ,特别是模糊不确定性进行分析 ;考虑设计变量取值的模糊性与大坝失效准则的模糊性 ,建立了在洪水和风浪共同作用下的漫坝模糊风险模型 ;然后研究该漫坝模糊风险模型的求解方法 ,即引入α水平截集的概念 ,经过模糊化处理后用常规的 JC法计算漫坝模糊失事概率。最后 ,对广西澄碧河水库的漫坝模糊风险进行了实例计算和评价。计算结果表明 ,随着防洪限制水位的提高 ,漫坝模糊风险也随之增大 ,当防洪限制水位从 185 .0 0 m提高到 186.90 m时 ,该大坝的模糊风险期望值在不考虑防浪墙的作用时为 6.0 3× 10 - 5,在考虑防浪墙作用时为 2 .698× 10 - 5,均小于其容许风险标准 7.12×10 - 5。据此 ,可将该水库的风险水位提高 1.9m ,从而增加兴利库容76.0 0× 10 6 m3。考虑漫坝风险的模糊性使失事风险的计算结果更加合理 ,风险评价更加符合工程实际 ,将模糊参数进行模糊化处理后 ,可直接采用现有传统风险计算方法计算失事概率。

This paper aims to present the authors' analysis of the overflow fuzzy risk on earth dam in the case of river or reservoir. In such cases traditional methods for risk analysis just take into account the randomicity of the variables in the design. But, in practice, fuzziness exists in both variables with the design as well as with the expectation of the dam's effective working life limit. Therefore, fuzzy theory should be introduced into the analysis of the risk on a dam so as to work out a fuzzy model of the risk on a dam through careful calculation of the fuzzy accident liability. In doing so, it is first of all to figure out the risk of accidents on the dam and the model of the fuzzy risk of overflowing the dam under the imagined interaction of flood and stormy wave. Then, further study is to be done to solve the model, in which the concept of α level-sectional gather is to be brought about. Immediately the model is made fuzzy, it would be the time to work out the probability of fuzzy accidents on overflowing by means of the normal JC method. And, finally, a trial calculation and evaluation has been done with the dam of Guangxi Chengbihe Reservoir as a case study example. The simulated calculation results show that the fuzzy risk on overflowing the dam conforms to the growth of the floodwater protection limit. When the maximum water limit goes beyond 185.00 m to 186.90 m, the expected value of fuzzy risk of the dam will be 6.03×10^(-5) when breakwater limit function is considered but 2.698×10^(-5) when the function is considered. Both of the risks are smaller than the allowable risk limit, 7.12×10^(-5). To conclude, the risk water limit can be brought up for 1.9 m so as to increase the storage of the reservoir which can produce benefits by 76.00×10~6 m^3. Considering the fuzziness in risk on overflowing makes the results of calculation more reasonable, and the evaluation on the risk closer to the reality. When all the fuzzy parameters are made fuzzy, current traditional method in calculating the risk can be used directly to work out the probability of the accidents. Therefore, the method the paper introduced is simple but practical, and therefore easy to be widely adopted.