Floor water-inrush channels induced by deep coal mining above a confined aquifer: theoretical analysis and experimental verification

The increasing probability and intensity of mine water inrush constrain the sustainable development of deep coal resources. A single mechanical model cannot fully explain how floor water-inrush channels form during deep coal mining above a confined aquifer. Therefore, two mechanical models were developed by considering strata dip angle, mining pressure, and hydraulic pressure. The mining-induced failure range and instability zones within the post-mining floor strata were compared to identify potential water-inrush channels. A physical similarity model experiment was used to observe floor failure and macroscopic channels above a confined aquifer and validate the accuracy of the mechanical models. Zones with larger mining-induced failure ranges in the shallow floor spatially coincided with high-risk instability zones in the floor aquifuge. Vertical connections between these zones preferentially developed into water-inrush channels. The locations, formation sequence, and quantity of floor water-inrush channels were correlated with the strata dip angle. These findings provide a theoretical reference for optimizing waterproof designs and deploying monitoring systems.