Stability analysis of a recurring soil slope failure along NH-5, Himachal Himalaya, India

The repetitive soil slope failure along the National Highway (NH)-5 in Jhakri region of Himachal Pradesh, India draws frequent concern due to heavy damage and traffic disruption almost every year. Being only linking route from border district to the nearby land area, stability of the road-cut slopes along this highway is of major concern in regard to safe transportation. Absence of any previous stability investigation of this recurring slope failure calls for an integrated geotechnical and numerical approach in order to understand the instability factors. The geotechnical analysis has been performed to determine the inherent properties of soil materials which affect the stability of existing slope. An event-specific antecedent rainfall threshold has been suggested to quantify the relationship between rainfall and slope failure. A two-dimensional limit equilibrium method has also been executed to visualize the scenario of pre- and post-failure stability of the slope. On the basis of limit equilibrium analysis, it has been inferred that slope geometry is a major affecting parameter that influences the failure pattern. Moreover, preventive measures through benching and soil nailing have also been proposed and validated through limit equilibrium analysis for long-term stability and safe transportation.