Stability Analysis of Partially Saturated Soil Slope by Random Limit Equilibrium Method

Abstract

Disregarding soil suction in computing the shear strength of unsaturated soils is widely used practice above the water table where the pore pressure is negative. Stability analysis was conducted using Rocscience Slide 2 software to evaluate matric suction contribution to the shear strength of the unsaturated soil in a slope in Hong Kong. The stability analysis resulted in a critical deterministic factor of safety for fully saturated soil and 1.2 when the matric suction is considered. Uncertainty in shear strength properties is considered by conducting multi scenarios probabilistic analysis. Lognormal distribution was assigned to the soil properties. The distribution was sampled 1000 times using Latin Hypercube method. A new sample was used to determine the safety factor in each simulation. Probability of failure (PF), mean safety factor (FSmean) and reliability index (RI) were determined in each scenario. It was shown that the most realistic results are obtained when cross correlation factors and correlation length (θ) are involved in the scenario. The study indicates that PF and RI are sensitive to a change in the correlation length less than 25 and less significant change beyond 25 m. The FSmean did not show noticeable fluctuation with the variation of correlation lengths.