Reliability Analysis of a Himalayan Rock Slope Considering Uncertainty in Post Peak Strength Parameters: Fid-Bau Portal

Reliability Analysis of a Himalayan Rock Slope Considering Uncertainty in Post Peak Strength Parameters

Tiwari, Gaurav / Gali, Madhavi Latha

Probabilistic analysis of a Himalayan rock slope supporting the piers of a railway bridge is carried out by considering strength drop from peak to residual strength. Importance of considering the uncertainty in post peak strength parameters for rock slopes in average quality rock mass is discussed. Ignoring the strength drop in post-peak strength parameters from peak strength parameters in the probabilistic analysis results in the overestimation of rock slope stability. Equations are used in this article to provide the peak and post-peak parameters of rock mass by considering peak and residual geological strength index (GSI). This method uses joint alteration factor, joint large-scale waviness, small-scale smoothness factors and block volume to calculate the peak and residual GSI values. Variability in the rock mass properties of a Himalayan rock slope is evaluated through these equations using Monte-Carlo simulation. Stability of the rock slope is analyzed through reliability analysis. Probability of failure was calculated by considering and ignoring a drop in post-peak strength parameters for the slope. Reliability analysis has been carried out using Hong’s point estimate method coupled with finite element approach. Results from the analyses showed that the considering a drop in post-peak strength parameters from peak-strength parameters have significant effect on the probability of failure and hence it is important to take into account the variability of post-peak parameters properly for evaluating performance level of rock slopes.