Evaluation of potential surface instability using finite element method in Kharsali Village, Yamuna Valley, Northwest Himalaya

Kharsali village, located in the Northwest Himalaya near the confluence of the Yamuna River and Unta Gad, is situated on a thick (>150 m) paleolandslide deposit. The village is continuously being eroded at its base by the two rivers. Cracks are noted in most houses while the ancient Shani Temple lying to the south of the village has tilted ~5° towards the northeast. Three slope sections (S-1, S-2, S-3) were modelled and analysed to determine the displacement and shear strain patterns of the slopes. Based on surface failure conditions, potential slope instability of the Kharsali village was evaluated from 2D Finite Element Method (FEM) using Shear Strain Reduction (SSR) analysis in the Phase2 software. Results indicate a critical Stress Reduction Factor (SRF) of 1.5 for the southern edge of the village (S-1) housing the Shani Temple. The development of failure surfaces at its lower portion signifies the propagating, progressive nature of the slope. The S-2 slope section is most vulnerable to slope failure, with a critical SRF of 1.08. This has been inferred by the formation of failure surfaces with displacements of 0.05–0.08 m. The S-3 section in the northern part of the Kharsali shows highest critical SRF of 2.76. The un-metalled road section in the north of the village near S-3 has developed a failure surface with displacement of 0.003–0.004 m, and a zone of subsidence. The S-3 section is relatively stable, whereas the S-2 section is the most vulnerable portion of the village.