Combined influence of rainfall and groundwater on the stability of an inner dump slope

Landslide is a commonly encountered natural disaster worldwide. Among the various influential factors, water is one of the major factors that can induce slope instability. The dynamic changes of rainfall and groundwater cause water migration inside the slope, which complicates the stress state inside the slope. This work aims at investigating the landslide problems that are induced by the combined action of rainfall infiltration and groundwater. The interaction mechanisms between the dynamic changes of rainfall, groundwater and the mechanical properties of the inner dump slope remain unclear, which make it very challenging to prevent landslide disaster in the open-pit coal-mine. To bridge this gap, we establish a theoretical model for the inner dump slope and experiment the impacts of various factors involved in the combination of rainfall and groundwater on the slope instability. An analytical solution of the safety factor (FoS) is then developed for inner dump slopes. The final slope safety factor is the minimum value of FoS in different layers. In the developed solution, the saturation theory and unsaturated theory are integrated on the slope mechanical model. The sensitivity study of FoS to the dynamic changes of groundwater, rainfall, and other potential primary factors inducing slope instability indicates that, there exists a critical wetting front and a critical groundwater depth, where the primary factors affecting slope safety changes. The critical wetting front depth ( h fo ) and the critical groundwater depth ( h wo ) can been obtained when the safety factor in the wetting frontis equal to the safety factor of the basement surface induced by groundwater ( F sf = F sj ). The natural layer depth ( h d = 15 m) is the critical turning point where the primary factor inducing slope instability changes from rainfall to groundwater for λ = 0.5 and h w = 5 m. The reliability and accuracy of the theoretical solutions are validated with a case study in Shengli #1 open-pit mine.