The main objective of the study is to estimate the shear resistance mobilized on the slope surface under large deformation and to identify the failure mechanism of the landslide through the simulation model. The field investigations were carried out using Geophysical tests, and the laboratory tests were conducted to identify the engineering properties of the soil with weathering characteristics of the parent rock. The residual shear strength parameters from Torsional ring shear tests were used in LS-RAPID numerical simulation software to study the mechanism of the landslide. The critical pore water pressure ratio (ru = 0.32) required for the initiation of a landslide was obtained. The increase in pore water pressure reduces the soil matric suction and thereby results in the reduction of the shear strength of the soil. The progressive failure mechanism and the three landslide processes (initiation, run out and deposition) are investigated. The velocity of the moving landslide mass in the role of demolishing the building is studied and helps in finding suitable remedial measures for the nearby building. The empirical rainfall threshold based on the antecedent rainfall was developed and revealed that either a high daily rainfall intensity of 142 mm without any antecedent rainfall, or an antecedent rainfall of 151 mm for a cumulative period of 5 days with even continuous normal rainfall can initiate landslide.

Rainfall-induced landslide is one of the major natural disasters in the Western Ghats of India. Kerala state in southern India received unprecedented heavy rainfall from July to August 2018. The rainfall received was higher than the average for the past 100 years. The present study discusses the investigation of vertical cut failure at Kaithakunda, located in Malappuram district, Kerala, India. It was due to the series of medium rainfall followed by a short period of extremely heavy rainfall. The heavy rainfall triggered the slope failure, which led to the damage of the building and the death of three residents of the building. The index and engineering properties of the soil were evaluated from the laboratory tests. The tests revealed that the soil was silty sand (SM) with low permeability. Tests on the mineral composition and microstructure fabric nature of the soil revealed that the soil was formed due to the weathering action of the parent charnockite rock. The finite element analysis of the slope was carried out using PLAXIS 3D. The analysis was carried out in two stages. The original slope before the vertical cut was modelled as the first stage. The vertical cut was modelled in the second stage to study the actual site condition before failure. The failure occurs due to the increase in pore water pressure in the soil, thereby reducing the matric suction and shear strength of the soil. The vulnerability of the building located near the cut slope is studied using the Support Vector Method to investigate the effect of material on the failure. The results showed the importance of the material properties in the increase of building resistance to 20%.