Landslide hazard assessment of residual soil slope using numerical simulation

Abstract

Landslide is one of the most severe natural hazards in the Himalayan Mountain ecosystem. Frequent and massive landslides may drain the economy of any region as a large amount of capital is invested, especially in slope treatment and rehabilitation of the affected people. The mountain slopes can be classified into two distinct categories based on stratigraphy, namely rock slopes and soil slopes. The rock slopes have highly fractured rock mass at the surface and are devoid of any soil cover. The failure in rock slopes is governed mainly by the discontinuities present within the rock mass. The soil slopes, on the other hand, are formed from the weathering of bedrock and are also referred to as residual soil slope. Slope failure in residual soil slope is a complex phenomenon involving various factors like slope topography, depth of soil cover, the grain size distribution of the soil, inherent heterogeneity in the geo-mechanical properties of the soil and presence of water. It was observed that when the slope is covered with a residual soil layer, the properties of the residual soil influence the overall stability of the slope while the effect of rock mass gets limited. In order to help the stakeholders, several Landslide Hazard Zonation (LHZ) maps were developed at various scales. However, these maps are primarily developed using limited input variables and remote sensing and GIS data. A detailed geotechnical based landslide hazard identification that had incorporated the variability of the geotechnical properties of geomaterial is found to be missing.When it comes to stability analysis of residual soil slopes, there are no specific LHZ maps available. Thus, an effort has been made to formulate Landslide Hazard Identification Chart for the residual soil slopes of the Lesser Himalayan Region formed from the weathering of carbonate lithologies. Another factor mainly ignored during landslide hazard assessment is incorporating post-failure debris flow analysis into the study. newline