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Abstract Aiming at the problems of complex geological conditions of coal seam, low efficiency of traditional drilling rig, difficult treatment of gas drainage borehole collapse area and low hole-forming rate, a precise detection and collapse treatment technology of coal seam based on pneumatic-hydrodynamic composite directional drilling technology is proposed. Through the pneumatic drilling tool to construct the coal hole section ( to avoid the expansion of mudstone in water ), the hydraulic drilling tool to construct the rock hole section ( to improve the drilling efficiency ), the borehole peeper is used to identify the characteristics of the coal-rock interface, and the DDZJ96 fixed-point grouting sealing device is used to accurately fix-point grouting in the hole collapse area to strengthen the stability of the hole wall. Based on Kriging interpolation method, a three-dimensional geological model of coal seam is constructed to guide the optimization of borehole trajectory. The field test shows that the drilling rate is increased to 87.5%, the gas extraction concentration is increased by 82.9%, and the effective extraction radius is 3.0 m ( pre-drainage for 90 d ). This technology provides an efficient and accurate solution for gas control in outburst coal seams.
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