Mechanical criteria and sensitivity analysis of water inrush through a mining fault above confined aquifers

Abstract

A mechanical model of water inrush through a mining fault in the workface above confined aquifers was developed according to ground pressure and strata control theory. Based on limit equilibrium theory of rock mass, mechanical criteria of the water inrush through the mining fault in the workface above confined aquifers were deduced by considering Mohr–Coulomb yield criterion. Five influencing factors, namely fault dip, fault cohesion, fault internal friction angle, suspended goaf range behind the workface, and thickness of floor strata protective zone, were selected from the mechanical criteria of an ultimate hydraulic pressure that the stope floor strata with a fault can tolerate. An orthogonal test was performed to analyze the sensitivity of the ultimate hydraulic pressure tolerated by the stope floor strata with fault. Results show that the fault dip and thickness of the floor strata protective zone significantly influence the ultimate hydraulic pressure tolerated by the stope floor strata with fault and represent 32.8% and 32.5% of the total effects, respectively. The fault cohesion, fault internal friction angle, and suspended goaf range behind the workface exert similar effects on the ultimate hydraulic pressure that the floor strata with a fault can tolerate and comprise 10.5%, 13.5%, and 10.7% of the total effects, respectively. The ultimate hydraulic pressure that the stope floor strata with a fault can tolerate decreases with the increase in the fault dip, fault internal friction angle, and suspended goaf range behind the workface but increases with the fault cohesion and thickness of the floor strata protective zone. This property decreases with the distance between the coal wall of the workface and the fault. This study provides insights into the water inrush mechanism through the mining fault in the workface and its corresponding sensitivity, thereby aiding in establishing the safe mining of coal seam with fault above confined aquifers.