Analysis on probability of water inrush and quicksand in different mining sequences under an unconsolidated alluvium aquifer by fluid-solid coupling theory

To study the behavior of overlying strata and the likelihood of water inrush and quicksand with different mining sequences under an unconsolidated alluvium aquifer, a numerical model based on the fluid-solid coupling theory was constructed by FLAC3D. Simulation results revealed that the mining sequences had a significant influence on the seepage, displacement and failure characteristics of the overlying strata. In this kind of geological and hydrogeological conditions, the workface close to the outcrop of coal seam easily suffers from water inrush and quicksand during mining. In the simulation results, the plastic zone, vertical displacement and pore water pressure in the overlying strata of the workface decrease more or less using the upward mining sequence than using the downward mining sequence. Therefore, the application of the upward mining sequence in the process of mining is preferential to prevent water inrush and quicksand.