Stability analysis and control measures of a debri landslide – a study along national highway of himalayan region
- Vol.59(1), Mar
- Roorkee Indian Society of Earthquake 2022
- 27-45p.
This study focused on the slope stability evaluation and providing suitable slope stabilization measures for the Kotropi landslide, that occurred on 13th Aug 2017 along NH 154 of the Padhar Tehsil, Mandi district, Himachal Pradesh. The landslide mechanism was complex and involved translational and rotational movement. The length and width of the landslide were 1155 and 190 m, respectively. Five soil samples were collected using the random sampling method for evaluating slope stability controlling properties such as direct shear strength, Atterberg limit, and particle size distribution. Soil classification revealed large quantities of pebbles and fine-grained particles (lean clay and silt). The results from particle size distribution revealed that soil size ranged from 4.75 to 2 mm and 0.42 to 0.15 μm in diameter and on an average comprised 44.5% of the soil sample. The 2D limit equilibrium model (LEM) was used for the slope stability assessment. the Factor of safety (FOS) was estimated to be 0.83, which proved the slope to be unstable even post-failure. Since the Kotropi landslide is located in the seismic zone IV, stability measures were checked under the influence of seismic loading in addition to rainfall conditions. Based on the Janbu simplified method, the FOS of the slopes reduced to 0.72 under the rainfall and seismic loading conditions which is well below the accepted limit indicating that the slopes are vulnerable post landslides. The proposed stabilization measure involves benching of slopes and reinforcing them with end anchorage techniques. Reinforced bench slope with end anchorage techniques have been suggested as the cost effective measure for post stabilization. A FOS values of 1.2 and 1.0 were achieved for rainfall and rainfall as well as seismic conditions proving that the proposed stabilization technique made the slope stable under both conditions.