The Research Of The Large Dam Risk Analysis Based On Grey-Stochastic Risk Probability

In the conventional method of setting safety factor assessment of dam ,the degree of safety can not be completely accurately characterized with the size of safety factor without taking into account the variability of design variables. Based on risk theory and the grey theory, this paper analyses dam risk of ShangShajiang Reservoir and adopts a more reasonable risk calculation model and risk analysis method to estimate several major dam accident risk probability, the main conclusion of the research are shown as following:(1) The mechanism and the causes of the hidden accident patterns of dam are analyzed and the possible hidden accident patterns are identified, the practical accident patterns are acquired by analyzing. The most likely failure building is the dam.(2)Based on the grey-stochastic risk theory, a risk model of slope failure of dam on the ShangShaJiang Reservoir is established. Based on the JC method, the grey-stochastic risk probability of slope failure can be calculated, the result is a risk interval [0.1285, 0.1503]. The grey-stochastic risk better reflects and measures the uncertainty of risk and it can offer more information than other reliability methods. For the stable evaluation of the dam slope discussed in this paper, the value of the safety factor, which is calculated by the traditional safety factor method, is 1.152. If K>1, that shows the dam slope is safe. However, considering the distribution of state variables and uncertainty of the dam slope system, the risk probability of the dam slope failure calculated by the grey-stochastic risk method still reach 12.85%～15.03%, so the degree of dam safety can not be completely accurately characterized with the size of safety factor.(3) Based on the grey-stochastic risk theory, a overtopping risk model of the ShangShaJiang Reservoir dam is established. The overtopping risk probability were calculated by using JC method in checking and designing flood level. If the height of the dam is 211.5m , the accident risk probability approximate zero. If in 210.5m (approximating the design specification height)and in design flood situation, the accident risk rate approximate zero, too. But in checking flood situation, the grey-stochastic accident risk probability is a interval [9.5479×10^-9,2.0085×10^-5].In the 1980s, the average annual overall accident probability of the dam is Pf =1.2710×^-4 in China. It is proved that the dam have greater potential to prevent flood and ultra-high security by the design specifications.