Area failure probability method for slope system failure risk assessment

Quantitative risk assessment of slope failure provides valuable information for slope reinforcement design and risk mitigation. Most of previous studies assessed the slope failure risk based on the critical slip surface with the minimum factor of safety. In general, the critical slip surface is unknown prior to the slope stability analysis and can vary with the underground soil profile. It was, however, observed in slope stability analyses that a slope may, simultaneously, fail along multiple slip surfaces. How to effectively incorporate multiple failure slip surfaces (MFSS) into slope failure risk assessment remains an open question. This paper develops a new method that provides an overview of the failure probability of soil masses at different locations on a slope, which is referred to as the area failure probability chart (AFPC) in this paper. Based on the AFPC, a general slope failure risk assessment framework is proposed to incorporate MFSS into slope failure risk assessment. The proposed approach is illustrated through a slope example. It is found that AFPC shows results of slope reliability analysis in a straightforward and visible way, which enhances the risk perception and communication for geotechnical practitioners, and ignoring MFSS leads to underestimation of slope failure risk.