Reliability analysis of unsaturated soil slopes

Many soil slopes are unsaturated in their initial state, and suction contributes to initial stability. Stability of these slopes decreases as suction decreases with time due to rainfall infiltration and water redistribution. Many of the parameters in the assessment of stability are highly variable. In this technical note, sensitivity/reliability analysis of design variables for a typical unsaturated soil slope is conducted. Sensitivity analysis shows that suction parameters have significant influence on the stability. Reliability computations performed for the slope considered show that failure zones are better captured by the reliability index than the conventional factor of safety. The study also shows that variation of saturated hydraulic conductivity significantly influences slope reliability.