First-order reliability analysis of slope considering multiple failure modes

This work studies the reliability analysis of a slope that considers multiple failure modes. The analysis consists of two parts. First, significant failure modes that contribute most to system reliability are determined. The so-called barrier method proposed by Der Kiureghian and Dakessian to identify significant failure modes successively is employed. Second, the failure probability for the slope is estimated on the basis of identified significant failure modes and corresponding design points. For reliability problems entailing multiple design points, failure probability can be estimated by the multi-point first-order reliability method (FORM), which gives the probability of the union of approximate events. FORM approximations at each design point and a subsequent series system reliability analysis are employed to estimate failure probability. Application of the procedure is illustrated through example problems. The results show that the applied procedure is able to efficiently consider various failure modes caused by stratifications and variations in soil properties in probabilistic slope stability assessments.