Reliability analysis of slope stability considering temporal variations of rock mass properties

Abstract

Temporal variation of rock mass properties, especially the strength degradation due to drying-wetting cycles as well as the acidic wetting fluid (rainfall or reservoir water) is crucial to stability of reservoir rock slopes. Based on a series of drying-wetting cycling and experiments considering the influences of pH values, the degradation degree models of the reduced cohesion CC', friction angle φ φ' are developed. 2D stability analysis of the slope is subsequently carried out to calculate the factor of safety (Fs) via limit equilibrium method (LEM) and a predictive model of Fs is built using multivariate adaptive regression splines (MARS), revealing the effect of the drying-wetting cycles and pH value. The reliability analysis by Monte Carlo simulation is performed to rationally consider the uncertainty and the temporal variation of the shear strength parameters of rock mass. Results indicate that the MARS-based model can estimate the Fs accurately. The Fs and the reliability index β decrease with increase of drying-wetting cycles, and the temporal variation of rock mass properties has significant influence on the slope reliability. Overlooking the temporal variation of rock properties may overestimate the Fs and reliability index β in the longer term.