Slope stability assessment of road cut slopes along NH 107 (Kund-Sonprayag), Gharwal Himalaya, India

Abstract

Slope instability is one of the major problems for the road cut slopes in the hilly areas. Detailed geological mapping with emphasis on the structural data can be a best approach to study these road cut slopes and helps to delineate the active failure condition of damage zones which are vulnerable. For the mitigation of these vulnerable locations, Structural mapping provides actual ground conditions of the study area. In the present study a 31 km road section has been mapped on 1:10000 scales. The major tectonic units and various thrust zones, shear zones and outcrop scale damage zones occurring in the study area are mapped. The major thrusts like Munsiari Thrust, Vaikrita Thrust and various discontinuities are marked in detailed geological mapping. In the study area 9 locations are identified which are prone to failure conditions. Various Geotechnical parameters including Slope Mass Rating (SMR), Basic Rock Mass Rating (RMRb) system and Geological strength Index (GSI) are calculated for vulnerable locations for slope stability assessment. Kinematic assessment of vulnerable locations categorized as toppling failure, planar failure and wedge failure. Calculation of Factor of Safety (FoS) of the affected locations provides values < 1. So, this study is mainly attributed to the Slope stability assessment which relates slope failures with Structural Damage zone. Based on the approach of Detailed Geological Mapping, FoS and Kinematic analysis, all the affected location of slope failures are occurring on the structural damage zones.