From Hill Cutting to Landslide: Understanding Failure of Himalayan Road Slope

Abstract

The expansion and widening of transportation corridors across the Himalayan range requires extensive excavation of naturally steep and geologically complex mountain slopes. Although road construction is essential for regional connectivity and socio-economic development, hill cutting fundamentally modifies the natural equilibrium of slopes and can transform previously stable terrain into highly vulnerable slopes. This review synthesizes the studies on the Himalayan rock cut slope from major transportation corridors, including National Highway (NH) -58, NH-7 and NH-09. The reviewed literature indicates that the failure process commonly begins with modifications to natural slope geometry during road excavation. Toe excavation can eliminate vital support, while steepening and over-heightening of cut slopes increase gravity-driven loads. Uncontrolled blasting and poor excavation techniques may also widen pre-existing discontinuities and produce secondary fractures, which would provide new release surfaces inside the rock mass. Exposure of recently dug rock surfaces over time encourages weathering, groundwater intrusion, and the deterioration of discontinuity conditions.