Further research on “three maps-two predictions” method for prediction on coal seam roof water bursting risk

In terms of the conditions of missed or thin coal seam direct roof impermeable layer and poor water yield ca- pacity of roof aquifer,on the basis of “three maps-two predictions” method,the roof aquifer water bursting risk evalua- tion method is further investigated from two aspects,one is roof caving and fractured degree,the other is roof aquifer water yield capacity. The roof caving and fractured degree is represented by the height of water-conducting zone. While the aquifer water yield capacity evaluation method is largely promoted on the theoretical basis of water-richness index method. On the one hand,the geology and hydrogeology investigation information,such as permeability coefficient, sandstone thickness,flushing fluid consumption,core recovery percentage and the thickness ratio of friable rocks to plastic rocks are used and regarded as the main controlling factors of water yield capacity. On the other hand,the few measured specific water yields are used to calibrate the evaluation result of the water-richness index method. The new method works out the problem of roof aquifer water yield capacity evaluation on the condition of low hydrogeology in- vestigation. In addition,the mine inflow of the mining workface is estimated on natural and artificial interference condi- tions by the DRN boundary condition of the Visual Modflow software. Finally,the Taigemiao coal field is taken as an example to show the detail operation steps of roof aquifer water bursting risk evaluation and mine inflow prediction.