Combined roles of saturated permeability and rainfall characteristics on surficial failure of homogeneous soil slope

Both rainfall characteristics (rainfall intensity and duration) and saturated permeability of soil may influence the type and mechanism of surficial slope failures. In general, the failures can be initiated by two mechanisms, i.e. loss of matric suction through propagation of wetting front, and rise of water table. Up to date, there are still no clear indicators to identify the dominant parameters that control the type of failure for these shallow landslides. This paper investigates the hydraulic responses of soils to the variations of rainfall characteristics and soil permeability through numerical analyses. The results showed that the hydraulic responses to rainfall for a homogeneous infinite slope underlain by an impermeable layer can be divided into two stages: 1) the propagation of wetting front, and 2) the rise of water table. Based on these hydraulic responses, the type and mechanism of failures were deduced from the analytical analyses. Both the rainfall characteristics and saturated permeability were found to be predominant in controlling the hydraulic responses of soil, and hence the occurrence time, depth of failure plane, and type of surficial slope failures.