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边坡稳定受到诸多不确定性因素的影响,比如土体性质的空间变异性以及地层情况的不确定性。这些不确定性因素的影响可以通过蒙特卡洛模拟(Monte Carlo Simulation,MCS)进行定量地分析。MCS概念简单并具有广泛的适用性。但是,在小概率失效区域内,MCS计算效率很低,需要庞大的随机样本量来保证一定的计算精度。本文提出了一种实用的边坡可靠度分析方法。通过采用一种高级的MCS方法(Subset Simulation,子集模拟)来提高小概率区域内的计算效率以及计算精度,并以EXCEL的表单环境为平台,联合使用VisualBasic Application(VBA)编写计算程序。在该程序中,子集模拟、边坡稳定的确定性分析和不确定性分析分别由三个相对独立的计算模块实现。最后,本文以James Bay土坝为例,简明地说明了所提出方法的有效性,并探索了临界滑动面的不确定性对边坡可靠度分析的影响。
The slope stability is affected by many uncertain factors, such as the spatial variability of soil properties and the uncertainty of formation conditions. The effects of these uncertainties can be quantitatively analyzed by Monte Carlo Simulation (MCS). The concept of MCS is simple and has wide applicability. However, MCS calculation efficiency is very low in small probability failure area, which requires a large random sample size to ensure a certain degree of accuracy. This paper presents a practical slope reliability analysis method. By using an advanced MCS method (Subset Simulation) to improve computational efficiency and computational accuracy in small probabilistic regions, a VisualBasic Application (VBA) program was developed using EXCEL’s form environment as a platform. In this program, deterministic analysis and uncertainty analysis of subsets simulation and slope stability are respectively implemented by three relatively independent calculation modules. Finally, taking the James Bay earth dam as an example, the paper concisely illustrates the effectiveness of the proposed method and explores the influence of the uncertainty of the critical slip surface on slope reliability analysis.