SEISMIC SLOPE STABILITY FOR LANDSLIDES

Abstract

Landslides are one of the major contributors of natural hazards due to ground failure. It occurs due to failure of a slope. Triggering mechanisms like excessive rainfall, earthquake or some man made activities (like production blast etc.) can cause a marginally to moderately stable slope to become unstable. Considering the fact that slope stability is a major reason behind landslide, it is necessary to analyse the stability of a slope before suggesting some remedial measures. As because analysing the stability of a slope is a large scale problem, so numerical simulation is the best technique to get a deeper understanding about the nature and behaviour of a slope. Mainly two types of slopes are analysed in this work. Natural hill slopes and rock slopes. Two natural hill slopes of Uttarakhand state of India, in Mussoorie and Nainital, are analysed with the help of Geostudio 2012 software products. Two types of analysis have been done. Limit equilibrium analysis and finite element stress-deformation analysis. In the limit equilibrium analysis, static and pseudostatic factor of safety values have been calculated by different methods and a comparative study is done between them. LEM based software SLOPE/W is used. The finite element stressdeformation analysis is done by using SIGMA/W and QUAKE/W software for the static and dynamic cases respectively. The results are presented in the form of stress and displacement contours. In the analysis of rock slopes, discontinuities possess a major role in its stability. Here, three types of analysis of rock slopes have been done. Slope under gravity loading, under excess rainfall condition and under seismic loading. In each of the analysis, parametric studies are carried out by considering different joint orientations. As distinct element method (DEM) is the best numerical technique for analysing a fractured rock mass, two dimensional DEM based software UDEC (Universal Distinct Element Code) 4.0 is used for all the analysis. The results are obtained in the form of factor of safety, displacements and block rotation. It has been found that out of plane joints are vulnerable towards sliding failure while in-plane joints are prone to toppling failure.