Deformation characteristics of unstable shallow slopes triggered by rainfall infiltration

Identification of the influence of hydrological and geological factors on slope deformation characteristics (i.e., the displacement–time relationship) under rainfall plays a crucial role in providing early warning information and enabling the implementation of emergency remedial actions before a landslide occurs. In this study, a series of coupled hydro-mechanical finite element analyses were performed to investigate slope displacement behavior triggered by rainfall infiltration. First, the numerical model was validated by comparing the predicted displacement with those measured from a full-scale landslide flume test. A parametric study was then conducted, considering various hydrological conditions and soil hydraulic and mechanical parameters that were statistically determined from a large soil database compiled from relevant literature. Further, the influences of the aforementioned factors on the timing, magnitude, and rate of slope displacement prior to landslide occurrence were quantitatively evaluated in a sensitivity assessment. The numerical results indicated that the slope deformation characteristics could be significantly influenced by various hydrological and geological factors. Nevertheless, the slope displacement over time for all cases generally can be divided into three stages, namely the constant, accelerated, and critical deformation stages, which correspond to various states of slope movement and pore water pressure development. The relationships of slope displacement magnitude and displacement rate with the factor of safety were established, which provide a valuable information in practice for engineers to interpret the slope stability level from a large quantity monitoring data of slope displacement.