Stability evaluation of spoil dump slopes reinforced by air-injection drainage from the perspective of reliability analysis

A spoil dump slope is a kind of artificial slope formed by the accumulation of engineering waste residue from multiple sources, which results in high variability of its mechanical properties. Large amounts of groundwater inside such a structure can make it prone to slope instability. Although an air-injection drainage method has been developed in recent years to reinforce common soil slopes by facilitating drainage, research involving the underlying mechanisms still needs to be further strengthened. In this study, a gas–water two-phase flow theory was applied for unsaturated soil seepage in a spoil dump slope, and the uncertainty of the spoil’s physical and mechanical properties was considered in a reliability analysis to evaluate the reinforcement effect of the air-injection drainage method. Based on a case study, the changes in reliability index and failure probability were determined before and after injection under different air pressures. The results show that air-injection drainage methods can provide effective reinforcement for spoil dump slopes by significantly reducing porewater pressures in a potential slip zone, thus reducing the possibility of slope failure. Moreover, a spoil slope reinforced by this method can better resist the adverse impact of rainfall.