Experimental Study on Process Optimization of Hydraulic Flushing in Downward Holes

In order to solve the technical problems of tight mining-excavation relay caused by the low efficiency of down-hole extraction and the failure of other auxiliary measures to achieve the better effect of eliminating outburst in the process of shield coal roadway excavation in Liulong Coal Mine, a hydraulic flushing test was conducted in the downward holes in No.7 coal seam in Liulong Coal Mine. The results show that: through using the technology of hydraulic flushing in downward holes, the average amount of coal flushed out by one downward hole can reach to 3 t to 5 t, the amount of coal bursting out of coal hole per meter is up to 0.5 to 0.8 t/m. It is proved that the hydraulic flushing in the downward holes can significantly improve the extraction effect of the adjacent boreholes in the affected area, the daily drainage concentration and percentage of pure gas capacity are enhanced greatly. By adopting the special process of hole sealing and gas drainage in downward holes, the high efficiency of boreholes by hydraulic flushing has been realized. The period of pre-drainage has shortened by about 3 times, and the safe and fast driving of coal lane has been achieved successfully.