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Himalayan Geology, Vol. 43 (2), 2022, pp. 435-441, Printed in India

Stability assessment of a weathered rock slope with surficial soil cover-A case study from Jaintia Hills, India


1Department of Applied Geology, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, India

2Department of Civil and Environmental Engineering, Indian Institute of Technology Patna-801106, Bihar, India

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Abstract: Hill slopes in the Himalaya and North-Eastern India hills often consist of a few meters of soil in the uppermost part underlain by weathered rocks that progressively transition to hard rocks. These slopes often cause shallow landslides and pose difficulties for stability evaluation due to their complex geo-mechanical nature. Such a slope along the hilly roads of Meghalaya, India, has been analyzed using a combination of empirical and numerical solutions and aimed to provide a methodology to solve the practical problem. The studied hill slope in the Rattachhera village of Meghalaya witnessed a landslide on 14th June 2015, which killed four people, injured two people, and stranded many vehicles on the road for more than 8 hours. The flanks extending on both the sides of the failed region are highly prone to failure as the slope mass consists of silty-sandy soil underlain by a weathered rock mass. Equivalent Mohr-Coulomb strength parameters of underlying rock masses were calculated from the Hoek-Brown failure envelope, and the soil properties were determined through laboratory testing. Finite element analysis of the Pre-failed slope under static load showed a complete failure condition with a safety factor of 0.8. The shear strain is as high as 7.2, and the total displacement is 12.8 m, validating the practical situation at the site. Possible stabilization measures have been proposed to stabilize the slope mass through soil nailing to avoid further adversity to the critical slope. Comparative results from numerical analysis of the pre-reinforced and post-reinforced model show a considerable reduction in shear strain and total displacement to nearly zero with the soil nail reinforcement. The remnant of the failed region may be stable under static and pseudo-static load.

Keywords: Himalayan slope, FEM, Static and Pseudo-Static load, Soil Nailing.

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