Stability of a 3D unsaturated vertical cut slope subjected to variable rainfall infiltration

Abstract

Rainfall infiltration is one of the main triggers of slope failure. Based on the upper bound theorem of limit analysis, this work presents an analytical stability analysis of a 3D vertical cut slope subjected to rainfall infiltration. An analytical model that can directly provide pore water pressure change at any depth and time is adopted to calculate the time-dependent matric suction and shear strength of unsaturated soil during the rainfall infiltration process. Thereafter, based on a 3D rotational failure mechanism of a slope, the energy balance equation is built, and the factor of safety (FoS) of the slope is consequently determined in conjunction with the strength reduction technique. The influences of the 3D characteristics of the slope and rainfall patterns on both FoS and failure pattern of the slope are investigated. It is found that the 3D characteristic of slope is a key factor which determines the FoS of slope. Different rainfall infiltration patterns lead to diverse variation rules of both the FoS solutions and the critical failure patterns of slope. However, these rainfall patterns with a same accumulated rainfall result in the same FoS solution of slope at the end of rainfall infiltration. The present work may provide guidance on the stability analysis and preliminary design of slopes subjected to rainfall infiltration.