Highly efficient drilling technique and matched equipment for soft and outburst-prone coal seam rich in FeS₂ nodules

Aiming at the problems such as shallow completed hole depth, difficult cutting discharge, low drilled ration of coal seams when drilling gas extraction holes by conventional air pressure drilling technology in soft and outburst-prone seam rich in FeS₂ nodules in working face 11080 of Yi'an mine, Henan Yi Coal Group, the composite cutting discharge mode in which the cuttings are discharged mainly by drill rod wings and subsidiarily by air pressure was put forward, through optimization of drill rig capacity and parameters of drilling tools, Φ95/60.3 mm plugged-in and sealing spiral rod and Φ98 mm arc bit were developed, the drilling technological parameters were formulated, forming a set of technology and equipment for drilling soft and outburst-prone coal seams rich in FeS₂ nodules. Through in-site industrial test, totally 8 boreholes were drilled, the maximum borehole depth was 103.5 m, the average borehole depth was nearly 97 m, the average penetration rate was 10.4 m/h, the net drilling efficiency was about 18.3 m/h, indicating that the technology and the equipment have good application effect for drilling similar seams.