弃土场边坡稳定性和可靠性的多工况对比分析

Comparative Analysis of Stability and Reliability of Spoil Dump Slope under Multiple Working Conditions

弃土场堆积体的物理力学性质是影响弃土场边坡稳定性的关键因素。由于弃土场边坡的特殊性,其坡体物理力学指标存在明显的变异性。基于可靠性理论,考虑关键指标的不确定性,将其作为随机变量,一定程度上可克服传统边坡稳定性分析中关键参数取值难以把握的缺陷。以贵州山区平罗高速公路某弃土场边坡为例,采用Spencer法、Morgenstern-Price(M-P)法和General Limit Equilibrium (GLE)法3种极限平衡方法分析了4种工况(天然、地震、极端暴雨、地震加极端暴雨)条件下该弃土场边坡的可靠性,分别得到各种方法在不同工况条件下的边坡失效概率和可靠度指标,并与常规的边坡稳定性评价结果进行了对比分析。结果表明:4种工况条件下该弃土场边坡常规稳定性分析与可靠性分析的评价结果基本一致,并且可靠性分析方法在边坡稳定状态的划分方面具有更高的分辨率,说明边坡可靠性评价结果比常规的边坡稳定性评价结果更为合理;当该弃土场边坡土层结构简单且破坏模式为圆弧滑动时,采用Spencer法、M-P法和GLE法3种极限平衡方法得到的弃土场边坡可靠性评价结果非常接近,这说明在实际工程分析中只需采用上述严格条分法中的一种方法,即可满足分析精度。

Physical and mechanical properties of the accumulation body are the key factors affecting stability of spoil dump slope.Due to particularity of composition of spoil dump slope, the physical and mechanical indexes of the slope have notable variability.Based on the reliability theory, the key indicators are considered as random variables.So, to a certain extent, it overcomes the defect that the values of key indexes are difficult to be determined.Taking the spoil dump slope of Pingluo Expressway in the mountainous area of Guizhou Province in China as an example, this paper analyzes the reliability of spoil dump slope under four working conditions(natural, earthquake, extreme rainstorm, earthquake combined with extreme rainstorm) by Spencer method, Morgenstern-Price(M-P) method and General Limit Equilibrium(GLE) method.Then the paper obtains failure probability and reliability index of each method under different working conditions, and makes comparison with the conventional stability analysis results.The results show that both stability analysis and reliability analysis of the spoil dump under four working conditions yield basically consistent results.However, the latter has higher resolution on the purpose of classification of stable state than the former, which indicates that the results obtained by reliability analysis are more reasonable than those obtained by conventional stability analysis.In addition, the case analysis also shows that when soil layer structure of the spoil dump is simple with circular sliding failure mechanism, the results yielded by the three strict limit equilibrium methods, namely, Spencer method, M-P method and GLE method, are very close, and any one of the above-mentioned methods can satisfy the analysis accuracy in a routine engineering application.