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.

A Preliminary Study of the Seepage Hammer Effect and Its Impacts on the Stability of Layered Infinite Slope

“…An interesting finding is that the cooperation of the seepage hammer effect and the Lisse effect might lead to a slope failure before the wetting front reaches the slip surface. Intense rainfall-induced change in pore air pressure and its impacts on slope stability has been a topic of concern recently [16][17][18]. This finding could be a potential research topic in the future.…”

“…Thus, changes in pore water/air pressure are a critical factor that contributes to landslides. Studies on the effects of rainfall on unsaturated soil in laboratory and field conditions using pore pressure measuring devices have been conducted by other researchers [5,6,11,[13][14][15][16][17][18]. Despite abundant field and laboratory data, many uncertainties remain with regard to the relation with pore water/air pressure change and rainfall infiltration.…”

“…In numerical modeling, a single-phase flow model based on the Richards equation was utilized widely to simulate the unsaturated flow in porous media [5,15]. The change in pore water pressure might be affected by the interstitial air, i.e., the Lisse effect, which is why the two-phase flow model was developed to simulate the dynamic behavior of pore air and its impacts on the pore water pressure [6,11,12,18,24,29]. To investigate the impacts of changes in pore water/air pressure on the slope stability, the limit equilibrium method evolved in the single-/two-phase flow model [18,30,31].…”

“…The change in pore water pressure might be affected by the interstitial air, i.e., the Lisse effect, which is why the two-phase flow model was developed to simulate the dynamic behavior of pore air and its impacts on the pore water pressure [6,11,12,18,24,29]. To investigate the impacts of changes in pore water/air pressure on the slope stability, the limit equilibrium method evolved in the single-/two-phase flow model [18,30,31]. The 1D slope stability analysis was widely simplified to applied infinite/finite slope theory [8,10].…”