## 1 Introduction  
During open-pit mining, as excavation proceeds to greater depths, surrounding groundwater gradually converges toward the pit and discharges naturally along the steep pit walls. Prolonged dewatering operations lead to a significant decline in the groundwater table, an increase in the thickness of the vadose zone, and the eventual formation of a groundwater drawdown cone [1, 2]. After mining operations cease and the open-pit mine is closed, the groundwater level gradually recovers [3]. Water storage and lake formation represent a cost-effective and practical approach for the rehabilitation of closed open-pit mines, balancing both ecological restoration and esthetic value [4, 5, 6]. However, the process of water impoundment may also give rise to a range of potential geological hazards. The increase in pore water pressure reduces the effective normal stress. This promotes the propagation of fractures within the rock mass and decreases the shear resistance of slope materials. Additionally, water can deteriorate the mechanical properties of slope rock and soil through various physicochemical processes. Theseinclude erosion, softening and disintegration, shrink-swell cycles, and frost heave [7; 8]. [PERSON] et al. [9] conducted slope similarity model experiments under varying rainfall intensities and water levels, and found a consistent pattern between pore water pressure and slope surface deformation. [PERSON] [10], [PERSON] [11], and other researchers analyzed extensive datasets including rainfall, water level, surface displacement, and deep deformation, and investigated the effects of seasonal rainfall and water level fluctuations on the stability of reservoir-related landslides. [PERSON] et al. [12] conducted coupled numerical analyses of drawdown-induced landslides based on landslide data from the Three Gorges Reservoir area and found that the delayed occurrence of sliding is often caused by the lag in pore pressure dissipation. [PERSON] conducted slope stability analyses under different water level conditions using the numerical software GeoStudio 2018 R2, incorporating hydraulic effects. Under certain water level scenarios, multiple areas were found to have potential landslide risks. [PERSON], [PERSON] [1] pointed out that the recovery of the groundwater level increases the pore water pressure within the slope rock mass, potentially submerging joint surfaces and thereby reducing their shear strength. During the pit lake formation process after mine closure, the coupled effects of stress and seepage can further deteriorate the slope rock mass, directly impacting slope stability [1]. The overall effect is that, over time, driven by factors such as glacial melt, rainfall, water level fluctuations, surface runoff, and groundwater activity, the pit walls may experience collapse or failure, posing risks to infrastructure or natural landscapes located above the pit [2]. Slope instability can lead to the release of additional mineral acidity and other oxidized products into the pit lake, resulting in water contamination. In extreme cases, significant slope failures may generate surge waves within the pit lake [13], which could even overflow the mine area and migrate downstream. The primary methods for evaluating slope stability include engineering geological analysis, limit equilibrium analysis, limit analysis based on plasticity theory, reliability analysis, and numerical simulation methods. [PERSON] [14] integrated numerical modeling, limit equilibrium analysis, and reliability analysis to investigate the landslide mechanisms and deformation characteristics of a large-scale bedding slope failure controlled by weak layers in the southern slope of the Fushun West Open-Pit Mine. He also analyzed the probability of slope failure after backfilling remediation. [PERSON] et al. [15] analyzed the deformation characteristics and failure modes of the Outang landslide under the influence of rainfall and reservoir water level using hydraulically coupled discrete element numerical simulations. [PERSON] et al.