Assessment of Risk along Rock Slopes in Himachal Himalaya using Rockfall Hazard Rating System and Landslide Possibility Index

ABSTRACT The rockfall and slope failure incidents increase during or after the monsoon season in hilly terrains. The challenging assignments for geologists and civil engineers are identifying the critical slopes and rockfall hazard zones. The present study reveals the rockfall and hazard-prone area of the slope sections along the National Highway-03 (NH-03), India. The well-known tourist destination along NH-03, which connects Mandi to Leh, is a major transit route with heavy vehicle traffic and a considerable risk of rockfall and slope failures. To assess the vulnerability and possibility of rockfall or slope instability, a comprehensive study was conducted together with detailed field investigations. The investigations show that the slopes, climate, geology, discontinuity conditions, and vegetation are key factors for the instability of slopes and rockfall conditions. The Rockfall Hazard Rating System for India (RHRSI) is applied to the slope sections along the highway and identifies the hazardous sections. The risk vs consequence graph revealed that the chosen sites fall either in the high risk-high consequence or high risk-low consequence zones. The Landslide Possibility Index (LPI) is also applied to evaluate the slope’s risk categories and hazard zones. Our study focuses on conducting an assessment of the rockfall hazard and the potential for landslides. Additionally, the study aims to analyse the parametric behaviour of rock masses, categorising them based on their susceptibility to rockfall and slope instability.