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This paper focuses on the risk of water inrush from the old goaf water of the upper coal group to the first mining face of the lower coal group under the condition of fully mechanized caving mining. Data from the 2101 working face of the No. 15 coal seam in the Wulihou Coal Mine were used to calculate the height of the water-conducting fracture zone on the first mining working face and the floor failure depth in the overlying No. 5 coal seam. An engineering geological model was developed, considering the lithological combination of the upper and lower coal groups, as well as the geological and hydrogeological conditions. Numerical simulations were conducted to analyse the deformation and failure characteristics of the roof and floor after dual-seam mining. The results revealed a floor damage depth of 12 m and a water-conducting fracture zone height of 109 m. Field monitoring data confirmed that after mining the 2101 working face, there was no water inrush risk from the overlying old goaf water into the No. 15 coal seam through the water-conducting fracture zone. The research results provide a reference for preventing water inrush accidents in similar fully mechanized top coal caving mining under the old goaf water. [ABSTRACT FROM AUTHOR]

The escalation of mining activities in the karst regions of Guizhou Province has heightened the occurrence of water-inrush incidents in deep coal mines. This study focused on water-inrush phenomena within the Xinhua mining area of Jinsha County, Guizhou Province, aiming to investigate the sources of these incidents. The findings indicated that the overlying limestone of the Changxing Formation in the coal seam served as a vulnerable aquifer under certain conditions, leading to water inrushes. The analysis of the spatiotemporal distribution patterns of water-inrush incidents at the working face indicated that previous mining operations damaged the shallow Changxing Formation limestone, resulting in the accumulation of goaf water and the formation of numerous mining-induced fractures. These fractures served as rapid conduits for water inrushes from both atmospheric precipitation and underground sources at the deep working face. The examination of surface water and mine water quality demonstrated that both exhibited similar characteristics, predominantly featuring bicarbonate, sulfate, and sodium compositions. Investigation into the relationship between mine water inflow and atmospheric precipitation established that atmospheric precipitation influenced the mine water supply cycle, with a replenishment period of ~10 months during the operational phase of the Jinyuan Coal Mine and about one month post-closure. The fractures induced by mining activities within the Changxing Formation limestone facilitated water flow, with atmospheric precipitation serving as the primary water source for the mine. This study offered a valuable scientific foundation for addressing water-related damage resulting from atmospheric precipitation in mines susceptible to water inrushes under analogous hydrogeological conditions. [ABSTRACT FROM AUTHOR]