Formation of pit lake and slope stability following mine closure: a case study of Fushun West Open-pit Mine

The Fushun West Open-pit Mine, recognized as Asia's largest open-pit coal mine, transitioned to a closure management phase following the cessation of operations in 2019. This study presents a quantitative analysis of the water inflow sources by meticulously reviewing historical data on the mine's drainage system and the hydrogeological conditions of the mining area. A numerical model representing the unsaturated-saturated groundwater dynamics was constructed to illustrate the spatial distribution of the groundwater flow. Employing the water storage analysis module within the WebGIS system, projections were made regarding the natural water accumulation process at varying water levels. The results indicate that, under natural conditions, an estimated 48 years would be required to reach a water level elevation of 50 m. However, this timeframe could be drastically reduced to approximately 3.3 years by implementing an accelerated filling strategy that channels water from the Hun River. Numerical simulations elucidate the failure mechanism of the water-sensitive slope on the northern bank during the water storage process, as well as the potential impact on the slopes above the water level. This comprehensive approach provides critical insights for managing decommissioned open-pit mines and optimizing water storage schemes.