Normally, the edge effects of surficial landslides are not considered in the infinite slope method for surficial stability analysis of soil slopes. In this study, the limit stress state and discrimination equation of an infinite slope under saturated seepage flow were analyzed based on the Mohr-Coulomb strength criterion. Therefore, a novel failure mode involving three sliding zones (upper tension zone, middle shear sliding zone, and lower compression zone) was proposed. Accordingly, based on the limit equilibrium analysis, a semi-analytical framework considering the edge effect for the surficial stability of a soil slope under downslope seepage was established. Subsequently, the new failure mode was verified via a numerical finite element analysis based on the reduced strength theory with ABAQUS and some simplified methods using SLIDE software. The results obtained by the new failure mode agree well with those obtained by the numerical analysis and traditional simplified methods, and can be efficiently used to assess the surficial stability of soil slopes under rainwater seepage. Finally, an evaluation of the infinite slope method was performed using the semi-analytical method proposed in this study. The results show that the infinite slope tends to be conservative because the edge effect is neglected, particularly when the ratio of surficial slope length to depth is relatively small.

通常情况下，无限边坡法在土体边坡地表稳定性分析中不考虑地表滑坡的边缘效应。本研究基于Mohr-Coulomb强度准则分析了饱和渗流作用下无限边坡的极限应力状态和判别方程。因此，提出了一种涉及三个滑动区（上拉伸区、中剪切滑动区和下压缩区）的新型失效模式。据此，在极限平衡分析的基础上，建立了考虑边缘效应的下坡渗流下土坡地表稳定性的半解析框架。随后，通过基于折减强度理论的数值有限元分析，使用 ABAQUS 和使用 SLIDE 软件的一些简化方法，验证了新的失效模式。新破坏模式得到的结果与数值分析和传统简化方法得到的结果吻合较好，可有效地用于评估雨水渗流作用下土坡的表面稳定性。最后，使用本研究中提出的半解析方法对无限斜率方法进行了评估。结果表明，由于忽略了边缘效应，无限坡度趋于保守，特别是当表面坡度长与深度之比相对较小时。使用本研究中提出的半解析方法对无限斜率方法进行了评估。结果表明，由于忽略边缘效应，无限坡度趋于保守，特别是当表面坡度长与深度之比较小时。使用本研究中提出的半解析方法对无限斜率方法进行了评估。结果表明，由于忽略了边缘效应，无限坡度趋于保守，特别是当表面坡度长与深度之比相对较小时。