Stability analysis of rainfall induced landslide

Abstract

Landslides represent one of the most common natural disasters globally. A landslide occurs when the stability of a slope is disrupted, often due to heavy rainfall, earthquakes, volcanic activity, or human activities like deforestation or construction. This disruption causes the soil and rock on the slope to lose cohesion and slide downhill. Rainfall-induced landslides can have devastating effects for the environment and human populations. While landslide-prone areas often experience recurrent occurrences, landslides can also occur in previously unaffected regions. In the current study, a new landslide was observed in March 2022 at Pangthang, East Sikkim. The study focused on a landslide in hilly terrain, collecting subsoil data and analyzing factors contributing to landslides. Using PLAXIS 2D software, stability analysis of the slope was conducted. Before construction, the slope was stable under fair weather conditions with a Factor of Safety of 1.331. After construction, including surcharge loads from superstructures, the slope remained stable under fair weather conditions with a Factor of Safety of 1.284. After heavy precipitation, landslides occurred exposing the foundation of a building. A nearby Jhora, and the middle of the slope adjacent to it, experienced failure. Considering the impact of a high infiltration rate of 0.12m/h, stability analysis using PLAXIS 2D software yielded a Factor of Safety of 0.95. To address the issue, an effective and affordable remedial measure was pursued. A sand drain was proposed to mitigate pore water pressure by capturing subsurface water and draining it from the bottom of the slope. Additionally, the slope was reinforced using concrete piles to enhance the shear strength of the weaker soil mass.