Numerical Investigation of Hill Slope Instability Due to Seepage and Anthropogenic Activities

Abstract

Stability analysis of slopes susceptible to different types of failure can be conducted using various prevalent techniques. Traditional limit-equilibrium (LEM) techniques, in spite of their recognized limitations, are the most commonly used evaluation methods. In this study, a finite element (FE) based stability analysis is adopted to assess the failure of an existing naturally stable stratified hill-slope located in the Umrangso region at Dima Hasao district of Assam, India. This paper illustrates the development of a FE model using Geostudio to simulate the real-field scenario of the progressive construction of various industrial manufacturing units which resulted in a massive mass movement of the slope. Cross-validation of the results from numerical analyses with that of the in situ observations successfully helped in the back-estimation of the most probable subsurface stratigraphy and location of water table at the site. The triggering stimulus that led to the instability of the slope has been aptly identified to be the addition of the workshop building load, which resulted in the drastic reduction of factor of safety (FoS) from 2.11 to 0.97. The seepage of rain water along the slope further aggravated the condition resulting in deformations that nearly approached the toe of the hill slope.