Mainak Ghosh Roy, Nirmal Singh, Sajan Moideen

Abstract: The paper reviews major geological problems encountered during construction of a mega hydropower project in the Lesser Himalayan region of Himachal Pradesh, India. Major hindrances encountered during construction of the project were backslope failure during construction of surface powerhouse in metavolcanics with slumped rockmass and rock bursting during tunnelling in hard and brittle quartzite. Two different modes of failures occurred during excavation of 180m long backslope of surface Powehouse-circular failure along highly weathered slumped rockmass and planar failure along crushed rock filled valley dipping joints. Stability assessment of powerhouse backslope was carried out through Finite element based software and Limit equilibrium based software for analysis of planar failure in jointed rockmass and determine critical slip circle of failure and Factor of Safety of the slope through strength reduction technique. Optimum support analysis for stabilization of cutslope was carried out through numerical simulation. Deformation meshes, accumulated principal strain and total displacement are the other parameters obtained from the results computed and analysed using FEM. The paper also back analyzes magnitude of in-situ stresses in rock bursting zones encountered during tunnelling using finite element based software to determine role of depth of overburden and field stress ratio in causing rock bursting. The result indicates that magnitude of principal stresses and yielding zones increase with depth of overburden and decrease in field stress ratios.

Keywords: Slope stability, Numerical analysis, Factor of safety, In-situ stresses, Rock bursting

Date Published: July 2, 2024
DOI: 10.11159/ijci.2024.006

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