The Effect of Discontinuity Orientation and Thickness of the Weathered Layer on the Stability of Lesser Himalayan Rock Slope

Abstract

Abstract The effect of discontinuity orientations and thickness of the weathered layer in the stability of jointed phyllite rock slopes of the Lesser Himalayan region was examined in this study. Numerical simulation was performed using the Rocscience RS2 V9 finite element software package. The performance of the slope was assessed for varying slope height, slope angle, weathered layer thickness, and orientation of the main joint and the cross joint set. The results indicate that the stability of rock slope depends on the relative orientation and distribution of the contained joint sets and the thickness of the weathered layer. Based on numerical simulation, the order of percentage reduction of a factor of safety (FOS) for the critical combination of joint sets has been identified. It was deduced that while keeping all the parameters constant, the effect of cross joint orientations is prominent in the case of shallow weathered layer and reduces as the thickness of the weathered layer increases. The effect of main joint orientations is prominent in the case of a deep weathered layer and reduces as the thickness of the weathered layer decreases. Analysis of variance (ANOVA) of the obtained result indicates that all the independent variables (slope height, slope angle, weathered layer thickness, main joint set, and cross joint set) are significantly predicting the dependent variable (FOS of rock slope) and the reducing order of significance is weathered layer thickness, slope angle, main joint orientation, slope height, and cross joint orientation.