Subsidence energy release and high potential energy water gushing mechanism of thick and hard rock strata in Binchang mining area

There is a Cretaceous Luohe Formation sandy conglomerate aquifer above the coal seam in the Binchang mining area, Shaanxi. This rock layer has the characteristics of large thickness, strong water - richness, large permeability coefficient, and large water head pressure. Moreover, the damage of the overlying thick and hard rock layer is likely to lead to the occurrence of high - potential dynamic water inrush. Combining the properties of the overlying rock layer of the Gaojiapu coal mine in the Binchang mining area, the development height of the water-conducting fracture zone, and the water inrush volume of the working face, the research on the energy release characteristics of the thick and hard rock layer fracture and the mechanism of high potential energy water gushing in the working face was carried out. The results show that the disaster-causing conditions of high potential energy water gushing are composed of “channel”, “water source”, and “force source”. Among them, the formation of the “channel” makes the “water source” migrate, and the water outflow from the working face changes from dripping to inrush. The formation of the “force source” provides water pressure for the migration of the “water source”, and increases the number of “channels” and the water conduction volume, making the working face change from water inrush to high - potential water inrush. During the disaster-causing process of high potential energy water gushing, there is an energy transfer relationship between the two dynamic processes of overlying rock fracture settlement and water migration. Through the derivation of the energy transfer equation, it is concluded that the dominant condition for inducing high potential energy water gushing is the fracture settlement of the thick and hard rock layer in the “force source”. In the energy conversion equation, the energy absorption value of the rock layer is negatively correlated with the energy absorption coefficient of the rock layer, the thickness of the broken layer, and the length of the broken layer’s dip direction, and positively correlated with the ultimate broken distance of the broken layer, and the energy value shows an exponential growth. Combining the change trend of the overlying rock energy and the change of the water inrush volume of the working face, it is found that in the interval where the water inrush volume increases, the stress and energy value of the overlying rock fluctuate greatly, and when the thick and hard rock layer breaks, the water inrush volume of the working face reaches the peak value, and the working face forms high potential energy water gushing. The research reveals the disaster-inducing mechanism of high potential energy water gushing, establishes the physical model of high potential energy water gushing, clarifies the relationship between various influencing factors, deduces the energy conversion equation of the fracture settlement of the thick and hard rock layer, explains the influence laws between different influencing factors and the energy absorption and storage value of the rock layer, and reveals the linkage relationship between the energy release characteristics of the fracture settlement of the thick and hard rock layer and the high - potential water inrush of the working face.