Foam drilling technology and application for broken and soft coal seams in underground coal mine
(2.Xi’an Research Institute of China Coal Technology & Engineering Group, Xi’an 710077)
【Abstract】Aiming at the limitation of middle-pressure air drilling for gas drainage in soft and broken coal seam, such as limited drill cutting removal capacity and dust pollution, the research on foam drilling technique in underground coal mines was carried out. CFD simulation of the flow field during the drilling process was conducted to obtain the optimized parameters of drilling tool structure for efficient drill cutting removal. Optimal structural parameters of wide-blade milled spiral drill rod with the number of spiral grooves as 3, the groove width as 26 mm, and the pitch as 110 mm were determined. A foam perfusion system suitable for underground coal mining was developed. Field test applications show that foam drilling technique and assorted wide-blade milled spiral drill rods have high efficiency of cutting transportation. Rotatory resistance was reduced in a range of 42%–48%. The technique can improve the drilling depth in soft and broken coal seam and provide a reference for drilling in similar deep coal mines.
【Keywords】 foam drilling; gas drainage; efficient drilling cutting removal; spiral drill rod;
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