边坡支挡结构岩土荷载的分项系数计算方法

岩土参数的变异特性给边坡支挡结构岩土荷载的确定带来困难,分项系数法考虑了可靠度,且计算简单,为此提供了解决方案。基于极限状态方程,将抗剪强度参数视为正态分布,采用一般分离法,通过分项系数的求解,推导了边坡支挡结构岩土荷载的分项系数以及荷载值计算公式;对单一滑面和折线型滑面两类典型滑面边坡案例分析表明:利用该方法能较容易地获得不同边坡目标可靠度指标值对应的支挡结构岩土荷载值;根据分项系数法计算得到的荷载值所设计的边坡,其由蒙特卡罗法获得的可靠度指标与目标可靠度指标存在一定偏差;其中,单一滑面边坡主要是负偏差,偏差最大约6%,对于折线型滑面边坡,当目标可靠度指标为1.65时,是负偏差,偏差约7%,但当目标可靠度指标大于1.65时出现正偏差。由分项系数法计算得到的支挡结构荷载值总体上安全可控。

Partial coefficient determination method for loadings of slope retaining structure

The geotechnical parameters of slope have great variability which makes it difficult to determine the load of the support structure accurately. The partial coefficient method,which considers design uncertainty and is simple to calculate, is capable of solving this problem effectively. Based on the limit state equation, this study takes the shear strength parameter as normal distribution,derived the calculation formulas of the partial coefficients and the loading of the slope support structure via the general separation method.Then it analyzed two typical slope cases:single sliding surface and polyline sliding surface, by using this proposed method. The results show that the loading values corresponding to the target reliability index of different slopes can be easily obtained;and there is a deviation between the reliability index obtained by the Monte Carlo method and the target reliability value by the presented method; for single slide slope, the deviation is mainly negative about 6%, while for polyline sliding type, when the target reliability index is 1.65, the negative deviation is about 7%, but when the target reliability index is greater than 1.65, the deviation became positive. Therefore, the load value of the retaining structure calculated by the partial coefficient method is generally unconservative.