Abstract: In order to improve outburst elimination of hydraulic flushing, the visco-elastic-plastic model of coal around boreholes considering plastic softening, dilatancy and rheological characteristic has been established, obtaining the parameter of relief ranges of different punching coal amount. At the same time the seepage-stress coupling model considering dynamic change of permeability and adsorption characteristics has been established, and the coupling model has been solved by COMSOL software. Drainage radius of different punching coal amount have been studied, and the boreholes space of hydraulic flushing coal has been optimized. The results show that relief range and drainage radius should be comprehensively analyzed in order to determine boreholes space of hydraulic flushing. When the punching coal amount is 0.5, 1.0 and 1.5 t/m, the relief range is 3.71, 4.61 and 5.8 m, and the drainage radius is 3.5, 4.3 and 5.0 m accordingly. Boreholes space of hydraulic flushing is determined to be 8.0 m because of the average punching coal amount of 1.0 t/m. The data of regional measures effect test and working face prediction show that the boreholes space is reasonable and reliable.

Key words: hydraulic flushing, multi-physics coupling, boreholes space, stress field, seepage field, drainage radius, relief range