| The hydraulic flushing is a kind of gas outburst prevention technological measure with wide applications prospects in the future, which make rock roadway as security barrier, after the seam-crossing borehole has drilled over, coal and gas are flushed out by the effects of incision from jet and impact of high pressure water jet, the stress around the borehole will drop down, and fissure stretch out,expand and induce with each other, the coal would have a full pressure-relief and permeability improvement in some range of the borehole, the effect of gas drainage will be improved and strengthened powerfully, to eliminate the risk of gas outburst from working face will come ture easily. In allusion to the coal seams characteristics of Huainan coal mine? soft coal seam,low permeability,high gas content and high gas pressure, particularly to the problem of low excavation rate and the conflict of exploitation and mining for the deep buried coal seams with low permeability and gas outburst danger, which have no protective seams to mine, in this article, in order to achive the rapid,safe and efficient excavation in the coal seams with serious gas outburst potential, by the method of combination of theoretical analysis,computer numerical simulation and field test, the theory of pressure relief and permeability improvement by hydraulic flushing was analysised, suitable technique parameters and process of hydraulic flushing for Huainan mining area was determined, influence radius for hydraulic flushing was investigated by the means of gas pressure and gas flow, and the range of its influence radius is about 3.5m～9.32m, compare the gas basic parameters such as the gas emission quantity,gas flow volume,damping factor of gas flow and the permeability of the coal seam pre-and-post hydraulic flushing, the effect of pressure relief and permeability improvement for hydraulic flushing was analysised, and the evaluation index system of pressure relief and permeability for hydraulic flushing in Huainan mining area was established. The theory of gas outburst elimination for hydraulic flushing was introduced, stress field distribution and the range of pressure relief around seam-crossing borehole in the condition of different distance between tow boreholes are simulated by the software of Rockscience Phase2, the technological parameters of the hydraulic flushing was optimized based on the storage situation of the 6-2 coal seam in Gubei coal mine.Validity of outburst elimination with hydraulic flushing was checked after hydraulic flushing carried out, the effect of gas drainage improved greatly, outburst danger potential is eliminated practically and efficiently , the driving speed of the working face is more rapidly than before, and the over standard rate of validity check index is reduced, working environment is greatly improved, and no gas dynamic phenomenon occurred in the driving process of working face, these fully demonstrate the validity and reliability of the hydraulic flushing.
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