强度参数的不确定性对土石坝坝坡失稳概率的影响

目前对土石坝坝坡的稳定性,主要是在坝料特性的确定参数基础上,采用极限平衡方法求出的坝坡抗滑稳定安全系数来评价。但实际的坝料特性参数往往是具有一定变化范围的变量,因此,安全系数大的坝坡不一定就比安全系数小的坝坡的失稳概率小。在分析研究12座均质土坝坝料强度参数统计特性的基础上,采用蒙特卡罗法对坝坡最危险滑裂面进行失稳概率分析,研究土石坝坝料强度参数的均值、变异性和相关性对坝坡失稳概率的影响。结果表明:强度参数的不确定性对坝坡的失稳概率有较大的影响,失稳概率随强度参数的均值的增大而减小,随变异系数的增大而增大。两个强度参数的相关性对坝坡的失稳概率也有显著的影响。由此可知,土石坝坝坡稳定性评价中,在确定性分析的同时,若能够考虑强度参数的不确定性,给出坝坡失稳概率,有利于更科学合理地评价土石坝的安全。

Influence of uncertainty of strength parameters on instability probability of embankment dam slopes

At present,the safety factor of sliding resistance determined by the limit equilibrium method based on the determinate property parameters of soils is used to evaluate the stability of the dam slopes.However,the property parameters of practical soils are variables with in a certain changeable range,so the instability probability of the dam slopes with a larger factor of safety is not always less than that with a less factor of safety.Based on studies on the statistical properties of soil strength parameters of 12 uniform earth dams,using the Monte-Carlo method to perform the dam slope instability probability analysis for the critical slipping surface,the influence of the mean value,variability and correlation of strength parameters of the fill materials of the dams on the instability probability of the dam slopes was studied.The results show that the uncertainty of strength parameters has significant influence on the instability probability of the dam slopes.The instability probability of the dam slopes decreases with the increase of the mean values and increases with the increase of the coefficients of variability of the strength parameters.The correlation between the two strength parameters also has evident influence on the instability probability.Therefore,during the evaluation of the stability of the embankment dam slopes,based on the deterministic analysis,if the uncertainty of strength parameters can be considered and the instability probability of the dam slopes can be calculated,the assessment of dam safety can be more scientific and reasonable.