Geotechnical assessment of cut slopes in the landslide-prone Himalayas: rock mass characterization and simulation approach

The roadway networks serve as arteries for the ongoing socio-economic activities within the Himalayan region. The perilous conditions of geologically active and fragile terrain are sustained threats to various disasters, including landslides. Large numbers of casualties and fatal incidence associated with landslides are being reported every year. The stability of road cut slopes is a crucial component for safer mobility and transportation activities. To attain a hassle-free and hazard-resilient design along the critical transportation route, a schematic and rigorous geotechnical investigation has been undermined. The present case study was undertaken to envisage cut slope stability and optimal designing of engineered slopes along the national highway-94 (NH-94) from Rishikesh to New Tehri, Garhwal Himalaya, India. The major issues associated with road cut slope failures are getting highlighted. Various rock mass classification systems including rock mass rating (RMR), slope mass rating (SMR) and its extensions, geological strength index, and Q Slope method were used to determine the prevailing stability. Stable slope angle without any reinforcement are suggested for the different probability of failure. Failure pattern was also assessed by applying kinematic analysis. Modified RMR for slopes is suggested by adjusting the orientation factor by using kinematic feasibility. Numerical simulation technique was also applied to determine safety factor. Exponential relationships are derived among Q Slope, SMR, and strength reduction factor. The guidelines to improve safety in terms of landslides are also suggested by considering the outcomes obtained by different methods.