Effects of coupled hydro-mechanical model considering dual-phase fluid flow on potential for shallow landslides at a regional scale

Abstract

A total of 36 rainfall-induced shallow landslides occurred on July 26 and 27, 2011, on Halmidang Mountain, Gyeonggi Province, South Korea. To precisely analyze these shallow landslides, a coupled hydro-mechanical model is applied that considers the dual-phase fluid flow of water and air and the deformation-dependence of the water retention behavior with hydraulic hysteresis. The changes in the pore pressures and saturations of the water and air are obtained from an infiltration analysis and are used to calculate the safety factor in a slope stability assessment. A comparison of the results from single- and dual-phase flow models is used to investigate the effects on the slope stability of the air flow and variations in the hydraulic conductivity resulting from the stress-strain behavior. The results suggest that considering the air flow in the hydro-mechanical coupling affects the increase rate of the pore water pressure, thus influencing the safety factor when ponding is more likely to occur during heavy rainfall. Finally, landslide assessments are conducted using the dual-phase flow model, which is slightly more consistent with actual landslide events than the single-phase flow model.