Influence of Toe Cutting on Seismic Response of a Typical Hill Slope in North-East India

In hilly regions of India, excavation of slope is a common practice for construction of roadways. Toe cutting of slopes is repeatedly carried out for construction of new roads or widening of existing roads with rapid growth in population needing urbanization. In earthquake prone hilly regions such as North Eastern part of India, seismic activity can play the role of a major triggering agent for catastrophic slope failure due to non-engineered and impromptu toe excavation. In majority of the cases, effect of toe cutting on hill slope stability under earthquake condition is studied based on Limit Equilibrium (LE) pseudo-static method, wherein the safety is measured in terms of a time independent single factor of safety (FoS) value. However, pseudo-static approach, in which earthquake is represented by a constant inertia force acting on the slope, cannot simulate the earthquake condition accurately and may overestimate the earthquake force. Hence, in this paper rigorous dynamic analysis is performed for safe and economical excavation of toe regions of the slope before road construction. The study reveals that the conventional pseudo-static analyses provide conservative results, which when used as a basis of mitigation measures, will lead to uneconomical stabilization technique.