Slope Stability Assessment of Rock Slopes Using Finite Element Modelling Along National Highway-5, Shimla, Northwestern Himalaya, India

Technology advances and rising population has led to the establishment of geoengineering projects such as dams, tunnels, bridges, road network, etc. in the mountainous terrain which causes slope destabilization. National Highway-5 connects Shimla, Kinnaur, Kullu, and China border to the rest of the country. The route is of paramount importance for defense and security purposes. The area encompasses complex geomorphological and geological terrain and often encounters road cut slopes susceptible to failure. In the present study, a detailed geotechnical investigation is carried out around Dhalli Landslide (September, 2017) and Malyana Landslide (August, 2018) along NH-5, Shimla, Himachal Pradesh. RMR, SMR, kinematic analysis and numerical modeling using the finite element modelling (FEM) technique is applied for the aforementioned two slopes and its nearby area. Kinematic analysis of joint data shows that rocks are prone to mainly wedge and planar failures. The RMR results show that the slopes belong to fair (Class III) and weak (Class IV) category. The SMR results for the slopes show that slopes lie in the completely unstable (Class V) category, unstable (Class IV) category and in the partially stable (Class III) category. The Strength Reduction Factor (SRF) was calculated using RS2 module of Rocscience. The SRF for both the slopes was less than 1 which shows that the slopes are completely unstable. Dominating factors responsible for the slope instability are identified and accordingly, some suggestions are proposed to strengthen the stability of road cut slope.