路堤边坡稳定可靠度计算中的模型不确定性分析

基于均质路堤边坡Monte Carlo法的稳定可靠度计算，分析了临界滑面搜索策略和稳定分析方法两类模型不确定性对边坡可靠度的影响特性，讨论了边坡失效概率随土工参数变异性的变化规律。研究表明，选用不同的临界滑面搜索策略所得可靠度结果差异不大，参数滑面法（overall slope）的失效概率略大于均值滑面法（global minimum），但差别对边坡稳定性分析没有实质性影响；土性参数变异水平是影响边坡可靠度的最重要因素，边坡在相同设计参数安全系数下的可靠度指标随参数变异性增大而急剧降低；不同稳定性分析方法对应的安全系数概率密度函数曲线形态基本一致，但失效概率差异明显，因此目标可靠度指标取值应与稳定性分析方法相适应。提出的考虑土工参数变异水平的安全系数取值修正原则，对改进确定性设计的边坡稳定分析技术有积极意义。

Analysis of model uncertainty for stability reliability of embankment slope

On the basis of reliability index of homogeneous embankment slope calculated with Monte Carlo method, the influences of critical slip surface searching strategy and stability analysis methods on slope reliability computation are analyzed; and the variation characteristic of slope failure probability with the variability of geotechnical parameters is discussed. The results show that: (1) Failure probability calculated by the critical slip surface searching approach of “overall slope” is slightly larger than by “global minimum”; but there is little substantial influence on analysis of slope stability. (2) The variability of geotechnical parameters is the main factor affecting the slope reliability; and the reliability index decreases sharply with increasing variability of parameters. (3) There is nearly same curve shape but various horizontal position of probability density function of safety factor approached with different stability analysis methods; and it result in significant difference of failure probability; so the target reliability index of design should correspond to the adopted stability analysis method. The principle that safety factor value should be modified by considering the geotechnical parameter variability is put forward; it may provide improvement conception to the traditional slope stability analysis which obtained with the mean value of geotechnical parameters.