Stability analysis of rainfall-induced landslides: A case study of a hilly area in Bangladesh

Abstract

Abstract This investigation examines the landslide due to rain in the Chattogram Hill Tracts of Bangladesh, including its origins, impacts, and the role played by the local geology and environment. Thus, designing early warning systems for such threats requires an in-depth understanding of the geo-environmental properties of soil slopes under heavy rainfall. In the past, when it rained more than 150–250 mm, localized slope collapses and large-scale debris floods occurred. Both extensive landslides and small-scale slope collapses have been seen. As a result, studies of soil-water characteristics have been conducted, followed by laboratory testing at the impacted sites. While hill cutting, deforestation, and unplanned human settlements contribute to landslide disasters, the study found that rainfall and soil type (fine-grained silt) were the most critical factors behind landslides. The slope stability equation was combined with a numerical model to pinpoint the issue's root. When it rains heavily, the soil becomes more saturated than usual, and its suction and shear strengths fall, as shown by analytical investigations and computer models. The slopes of the hills become precarious as a consequence. However, the mechanism has been demonstrated, considering some simplified assumptions. In contrast, it has been noticed that most of the landslides occurred when the degree of saturation was maximum and the safety factor was nearly 0.4 to 0.9; on the other hand, the safety factor was 1.8 to 2.0 in the dry condition. These experimental findings might be implemented in early warning systems for flash floods and landslides.