Study On The Technology Of Pressure-relief Gas Extracting From Upward Borehole In The Lateral High Drainage Roadway

To solve the problem of upper corner gas overrun in two adjacent working face, based on the geological conditions of the Liyazhuang coal mine No.2-603 working face, the paper took the coal mining pressure-relief gas in the No.2-603 working face overburden rock as the research object, the technology of pressure-relief gas extracting from upward borehole in the lateral high drainage roadway was systematically analyzed by laboratory experiments, theoretical analysis, numerical simulation, field test and industrial experiment methods etc, the analysis of mining-induced fracture development features of mining overburden rock and the end position of upward borehole in the lateral high drainage roadway was emphatically analyzed, and the arrangement parameters of upward borehole was determined, which effectively solved the problem of working face upper corner gas overrun and guarantee the safe and efficient mining of working face. The following main conclusions are drawn.(1) No.2-603 working face roof lithology is mainly hard rock,theoretical analysis, numerical simulation, borehole peep and industrial experiment analysis methods were used to show that the height of caving zone was 7.8m to 12.2m and the height of fissured zone was 32.8m to 44 m.(2) The law of overburden fractures evolution after mining showed the working face upper end of overburden mining fissure present "partition" concentrated distribution, the first area from the coal seam floor was 13 to 25 m, width was about 65 m, distance of goaf boundary was 12m; the second area from the coal seam floor was 38.6 to 50 m, width was about 50 m, distance of goaf boundary was 28m; and which was 62 degrees or less of mountain mining dynamic angle. first area was close to the working face, where there was more serious air leakage; according to gas lifting and floating features, gas was mainly concentrated in the second area; therefore, it was necessary to arrange the end position of upward borehole in the second area.(3) Put forward the way of arranging the lateral high drainage roadway, which meant that the high drainage roadway is located on the outside of the No.2-603 working surface(the high drainage roadway is located on the inside of the No.2-605 working surface), the high drainage roadway can serve to drain the coal mining pressure-relief gas in two adjacent working face overburden rock, so as to reduce the two adjacent upper corner gas concentration and solve the problem of gas overrun in two adjacent face upper corner.(4) The gas drainage results of experimental borehole showed that the reasonable end position of the upward borehole was located in the 44 m of the coal seam roof, and the projection length of the borehole in the mining area was not less than 28 m.(5) The upper borehole gas drainage concentration was 10%~65%, the production class and overhaul class of the No.2-603 working face monitored upper corner gas concentration were respectively 0.50% to 0.95% and 0.47% to 0.89%. The application results showed that the end position of the upward borehole was reasonable, and the arrangement of the upward boreholes effectively draw the No.2-603 working face overburden rock mining pressure-relief gas.