Upper-Bound Limit Analysis of Unsaturated Soil Slopes under Rainfall

Abstract

This paper presents an analytical framework for the stability analysis of unsaturated soil slopes under rainfall. The conventional log-spiral upper bound limit analysis for dry and saturated soil slopes is extended to unsaturated soil slopes by incorporating matric suction and rainfall infiltration. For an unsaturated soil slope under rainfall, shallow translational failure may be more critical than rotational failure. Hence, a translational failure mechanism in the context of upper bound plasticity theory is proposed, and its effectiveness is validated by finite-element analysis. Through the dimensionless stability charts developed by the upper bound limit analysis, the controlling factors on the failure mode of unsaturated soil slopes under rainfall are identified and investigated.