Failure Mechanism and Movement Characteristics of Overlying Strata in Longwall Mining Face with Thick Aquifer

The failure and movement of overlying strata with a thick aquifer are closely related to the water-inrush pressure and the hydraulic coupling in coal mining faces. However, there is limited research on the large-scale failure mechanism and displacement law of overlying strata by considering fluid–solid coupling. In this study, taking Daojiao coal mine as an engineering background, the failure mechanism and movement characteristics of overlying strata with a thick aquifer are comprehensively investigated after considering fluid–solid coupling by means of theoretical analysis, large-scale physical simulation, and numerical simulation. The results show that seepage and water pressure can significantly affect the overlying strata-movement parameters that the initial and periodic breaking distances of the aquifuge under the action of hydraulic coupling increase with the increase of the tensile strength of rock, and the decrease of hydrostatic head. In addition, the overlying strata of thick aquifer can be regarded as tensile failure based on the simulation results. The overlying strata above the goaf generally sinks downward with a funnel shape, and the main roof periodically appears to be a cantilever-beam structure. Moreover, the periodic breaking distance of the aquifuge is about half of the initial breaking distance, which is consistent with the results of theoretical analysis.