Risk Assessment of Slope Failure by Representative Slip Surfaces and Response Surface Function

This paper develops a quantitative approach for risk evaluation of slope failure based on a finite number of Representative Slip Surfaces (RSS) with Limit Equilibrium Method (LEM). A second order polynomial response surface function (RSF) is calibrated for each RSS in order to improve the computational efficiency. The volume of sliding mass associated with each RSS is a measure of consequence of slope failure along this RSS. The risk of slope failure is evaluated by Monte Carlo Simulation (MCS) and the contribution of each RSS to risk of slope failure is quantified. Thus, the risk of slope failure is de-aggregated into each RSS. The proposed methodology is illustrated through a three-layer cohesive soil slope. The de-aggregations of probability of slope failure, p(f), and risk of slope failure, R, are conducted at different scale of fluctuations, and the results for de-aggregation of p(f) are compared with those for de-aggregation of R. The comparison indicates that the group of key RSS that dominate p(f) differ considerably from those that dominate R. These different groups of key RSS may lead to different strategies in the subsequent risk mitigation, if any. The proposed approach provides an efficient and quantitative tool for identifying the key group of RSS in the planning of slope risk mitigation.