Geotechnical investigation and numerical analysis of slope failure; a case study of landslide vulnerability zone in Kolli Hills, Tamil Nadu

Landslides are the downward movement of materials under the influence of gravity when shear stress exceeds the shear strength of the material. It includes various movements resulting in complex type of slope failures which commonly occurred on cut slopes of Ghat roads in mountaneous region. The study area chosen for the geotechnical investigation is Kolli hills situated in the tail end of the Eastern Ghats in Namakkal district of Tamil Nadu, India. The ghat road section of 20 km stretch along with 70 hairpin bends, connects the foothills at Karavallikkombai to Sholaikkadu at the top is selected for the present study. The hill is situated at a fault zone which is extended from Mettur dam, Salem district, Tamil Nadu. In this study, undisturbed soil samples were collected from 10 landslide locations and tested for its index and engineering properties. Based on the test results, static slope stability analysis using Modified Bishop method and dynamic slope stability analysis using Simplified Newmark method were carried out to find out factor of safety of the slopes which is used to derive the slope stability assessment of the study area. The landslide hazard zone assessment was carried out to identify the landslide prone areas.