Landslide events are one of the commonly experienced natural disasters in Hong Kong that often cause enormous economic losses and threaten public safety. Among various mechanism causing landslides, infiltration from rainfall is the main one that leads to slope failure. Therefore, modeling of rainwater infiltration and prediction of pore water pressure distribution in both saturated and unsaturated soil are essential in determining the stability of a slope....[ Read more ]

Landslide events are one of the commonly experienced natural disasters in Hong Kong that often cause enormous economic losses and threaten public safety. Among various mechanism causing landslides, infiltration from rainfall is the main one that leads to slope failure. Therefore, modeling of rainwater infiltration and prediction of pore water pressure distribution in both saturated and unsaturated soil are essential in determining the stability of a slope.

The conventional approach in modeling flow behaviors in steep slopes is to decouple the surface and subsurface flow processes. However, infiltration is affected by the temporal and spatial variations of the subsoil condition and surface runoff depth. To improve modeling the rainfall-infiltration-runoff process it is desirable to simultaneously consider the interactions between surface and subsurface flows. Very little research has been done on coupling both surface and subsurface flow processes to predict the pore-water pressure distribution in slope stability analysis. Therefore, this study attempts to apply and examine a coupled surface-subsurface flow model, in conjunction with the slope stability analysis, to simulate the rainfall-infiltration-runoff-slope stability process.

In addition, uncertainties exist in all aspects of surface-subsurface flow modeling process. The surface roughness, soil-water retention characteristics, as well as shear strength properties are all subject to uncertainty. As a result, the corresponding model outputs are also subject to uncertainty. Therefore, uncertainty and sensitivity analyses are employed to analyze the effects of model inputs on the model outputs. Reliability analysis is also performed to quantify the failure probability of a slope. It is found that slope angle, initial moisture condition, and shear strength properties are the major factors contributing to the uncertainty of determining the safety factor. Saturated hydraulic conductivity and air entry parameter (α) are the two main parameters affecting the flow behaviors and soil moisture condition as well as the pore-water pressure distribution.