Influence of Hydrologic Behavior in Assessing Rainfall-Induced Landslides

Rainfall-induced landslides constitute a major risk globally to the built environment. Practically all traditional slope stability analyses that include rainfall influences do so by varying the groundwater flow patterns with increasing pressure heads and often a rising groundwater table. Rainfall infiltration inside soil slopes result in changes to the hydrologic behavior of the soil. Critical conditions within the hydrologic behavior correspond to failure of slopes. A better understanding of the influences of the hydrologic behavior on landslide mechanics is therefore of significant geotechnical focus. This study investigated hydrologic behavior by performing an unsaturated slope stability analysis for several published case studies. This study used a fully coupled hydro-mechanical analysis with time-dependent boundary conditions to evaluate the case data. Although the hydrologic behavior was described by the wetting and drying soil-water characteristic curve (SWCC) behavior, the wetting SWCC was estimated using only the drying data. A factor of safety analysis for the case histories was performed at their final stages. The findings from this research show the wetting SWCC parameters have greater influence on the hydrologic behavior of a slope during rainfall, when compared to drying SWCC parameters.