土坡稳定分析最小折减安全系数评价体系研究

借助简单均质土坡安全系数精确解析式,采用最优化方法的枚举法搜索最小可靠指标βmin和安全系数Fsmin(及对应的可靠指标βFmin)。对安全系数法和可靠指标法两大评价体系以及βmin和βFmin的相互关系和差异性等方面进行了例证比较分析,同时揭示了传统条分法(GLE法)计算值的保守性以及在某些滑弧出现反翘(即存在被动土体区域)情况下对滑弧形状的判断失误。考虑土性参数分布类型及变异特征的影响,利用Monte-Carlo法求解各个假想滑弧的安全系数Fsi和失效概率Pfi,并以Pfi对Fsi进行折减(定义为折减安全系数FsRi=Fsi(1-Pfi))建立了以最小折减安全系数FsR=min(FsRi)为评价标准的边坡稳定联合评价体系。通过典型算例证明该评价体系与文献中的二元指标体系有很好的一致性。

Reduced safety factor evaluation system for soil slopes

Based on the accurate calculation formulae of safety factor,the minimum reliability index(βmin) and the minimum safety factor(Fsmin)(with the reliability index βFmin) of simple soil slopes are searched directly.The difference between the safety factor method and the reliability index method,and the relationship between βmin and βFmin are investigated.The results reveal that the traditional slices method(GLE method) is conservative,and it may give an unrealistic evaluation,especially for the circle arch surface failure with resisting soil part.Considering the probability distribution type and variable characters of strength parameters,the safety factor(Fsi) and failure probability of each slip surface are calculated by use of Monte-Carlo method.And the reduced safety factor is given by FsRi=Fsi(1-Pfi).A slope stability evaluation system is founded using the minimum reduced safety factor FsR=min(FsRi).Several typical examples are studied.The results show that the evaluation system is in good agreement with the dual index system by others.