Stability appraisal of road cut slopes along a strategic transportation route in the Himalayas, Uttarakhand, India

Abstract

In precarious mountain terrains like the Himalayas, road cut slopes are highly vulnerable to slope failures. Slope failures in the region are often triggered by natural factors such as neotectonism, rainfall, seismicity, weathering, erosion, etc. However, rapid human intervention is an additional factor causing large-scale slope instability in the region. Unplanned excavations of slopes for construction and/or widening of roads decrease slope stability. The inevitable slope failures cause major inconvenience to tourists and residents and are also responsible for severe injuries and loss of lives and property. The present study incorporates a stability analysis of road cut slopes along National Highway 58 (NH-58) from Kaliyasaur to Rudraprayag, Uttarakhand. Vulnerable slopes were identified during the field survey. To evaluate stability conditions of rock mass, rock mass classification systems including rock mass rating (RMR), continuous slope mass rating and the Geological Strength Index (GSI) were employed to identify different stability grades. Furthermore, quantified GSI was correlated with basic RMR in a bivariate plot, which showed a linear relationship. Kinematic analysis was also carried out to identify the probability of structurally controlled failures due to adversely oriented discontinuities. Outcomes from different methods corroborated each other and matched the existing site conditions.