Failure characteristics of overburden rock (soil) and sand control technology in high strength mining of shallow coal seam

With the large-scale and efficient mining of coal resources in China,local caving and bench convergence accidents frequently occur in the mining area with thin bedrock and shallow depth,which cause serious water resources and environmental damage. However,the mining failure rules of bedrock and clay aquiclude combination structure are different to traditional rock strata because of continuous clay layer,which will provide conditions for the prevention and treatment of mine water inrush and water preserved mining. In this paper,the methods of numerical simulation and theoretical analysis were conducted to simulate the basic characteristics of overlying rock (soil) fracturing and roof breaking movement under the “ clay aquifuge-bedrock weathering zone-bedrock” with different clay layers and bedrock thicknesses. Therefore,the failure characteristics of overburden rock (soil) and height of development were obtained, the sand inrush disaster factors and prediction criterion were analyzed,and the technical means of prevention and control of water inrush of sand were accordingly proposed. The results show that the overlying rock (soil) damage development height and characteristics were varied because of the control effects of different bedrocks and soil thicknesses under the condition of “ sandy-soil-rock type of overlying strata” in the shallow buried coal seam. Water and sand, channel,power source,and space were the main factors causing the disaster of water inrush of sand in unconsolidated aquifer. The prediction criterion of sand inrush has been proposed. The sand inrush disaster of shallow coal seam was controlled through preventing roof cut,pumping aquifer head pressure,locally grouting and fixing sand and reasonably retaining the coal rock pillar.