Influence of Rock Strength Variability on the Stability of Potential Planar and Wedge Discontinuity Shear Failures

The stochastic approach to discontinuity shear strength (StADSS) avoids scale effects by predicting peak and residual shear strength of natural rock discontinuities using full-scale discontinuity data. Until recently, like many shear strength models for natural rock discontinuities, StADSS assumed that the strength of a rock mass is uniform despite its known variability. The variability of rock strength is often overlooked but should be incorporated for a rigorous slope stability analysis during the design and hazard mitigation of transportation corridors. This paper proposes a methodology to incorporate variable material strength to StADSS, and its resulting influence on predictions of peak and residual shear strength of discontinuities for case studies with increasing levels of roughness. Within StADSS, a unique set of strength parameters was assigned to each iteration of the Monte-Carlo simulation to account for the inherent variability of rock strength in the prediction of shear strengths. Observations from analysis have shown that the variability of rock strength parameters influences predictions of shear strength in different manners. The type of influence on shear strength predictions was unique to the varied parameters, the level of roughness of the discontinuity, and the normal stress applied. The significance of variation has highlighted the importance of investigating the sensitivity of slope stability to various stochastic input parameters, including the natural variability of the rock material strength.