A novel subroutine for estimating unsaturated slope stability considering water fluctuation in spatially variable soils

Safety of the reservoir slope under water fluctuation has attracted increasing concern in geotechnical engineering over the recent years. The main objective of this study is to estimate the unsaturated slope stability under water fluctuation. A user-defined ABAQUS Subroutine is developed to simulate various dynamic water fluctuation conditions. In this study, both the deterministic and probabilistic analyses are conducted to estimate the unsaturated slope stability under dynamic water fluctuation. Results show that there is a hydraulic hysteresis for the saturation line inside the slope and the water rising condition is the most dangerous case. Compared with the deterministic model, it is found that neglecting the spatial variability of soil strength parameters will produce overestimated safety factors during the water rising and rising-constant-falling process. As for the water falling period, the unsaturated slope stability may be underestimated except at a low falling velocity (i.e., 0.1 m/d) when ignoring the spatial variability. Therefore, it is recommended to take the inherent spatial variability of soil strength parameters into account when estimating the reservoir slope stability.