Exploration on gas drainage technology and equipment of fracture zone in coal seam roof

The gas over-limit issue in the upper corner of the gob and the return air entry needs to be solved urgently. In order to drain the gas in the fractured zon e of the gob and reduce the gas concentration,a high-position directional long borehole is proposed to replace the traditional high-drainage roadway to control the gas i n the upper corner of the gob. The effect of high-position directional dilling diameter,layer height,depth,etc. on the gas drainage effect in the fractured zone is verified b y a case study of the large-diameter directional drilling machine ZYWL-13000 DS drilling in the 33( 4) 13 working face of Shuangliu Coal Mine. The results show that:① The diameter of the directional borehole has a great influence on the efficiency of gas drainage. Therefore,the largest possible borehole diameter should be selected wh en the geological conditions and the performance of the drilling rig permit; ②The 5 ~ 8 times the mining height of the coal roof is a more suitable construction level for directional drilling; ③Without collapsing the hole,with the depth of the directional drilling,the gas drainage effect gradually improves,and with the mining of the coal min e,the gas gushing from high-level drilling will be in a balanced state. The case analysis shows that: in the case of directional drilling of 4 holes and 1 hole failure,the tot al amount of gas drainage is only 2 m3/min lower than that of the high-drainage roadway,but the application of high-position directional long drilling technology for gas d rainage can make the cost reduce by more than 70%, and the effective construction period is shortened by more than 75%.