Slope stability analysis of the Rangamati District using geotechnical and geochemical parameters

Landslide and human mortality have been a common phenomenon in the Rangamati district over the past several years. This study examined the geotechnical properties (e.g., grain size analysis, plasticity index, liquid limit index) and geochemical properties (e.g., erodibility index, weathering index, K factor value, redness rating) of the soil in order to determine the causes and vulnerability of the landslide. Three types of soils (sand, silt and clay) have been classified based on grain-size distribution for geotechnical and geochemical analyses. The geotechnical properties of the soils examined indicate that most soils are sandy loams, of poor quality and plastic in nature. Geochemical properties show that the weathering index is higher for the clayey soil which is about 3.65 and the erosion index is higher found in the silty soil of ~ 6.7. The stability index is very low (~ 0.06), and the K factor value is higher 0.046 for the non-cohesive sandy soil which indicates high susceptibility of landslide. Numerical analysis based on geotechnical properties of the soil indicates that the steep slopes are even stable at the dry condition, while it is in risk at wet condition. A bio-engineering approach was proposed which showed that local plants could withstand and render stable in the barred slope in a few years.