Instability of unsaturated soil slopes due to infiltration

This paper presents a procedure for calculating the safely factor for an un saturated slope suffering from rainfall infiltration. The process of infilt ration into a slope due to rainfall and its effect on soil slope behavior w ere examined using a two-dimensional finite element flow deformation couple d analysis program. The modified Mohr-Coulomb failure criterion was adopted for unsaturated soil strength to consider variations in strength due to th e presence of matric suction. A safety factor was calculated based on the s moothed stress field obtained from finite element analysis, and an optimiza tion technique was used to search for a critical slip surface. Some numeric al examples are analyzed. The results illustrate a typical process of infil tration into unsaturated soil slopes and the effect of hydraulic conductivi ty on slope stability during rain-induced infiltration. (C) 2001 Elsevier S cience Ltd. All rights reserved.