Application Research on Roof High Position large-diameter Directional Borehole of Sanyuan Coal Mine
To verify the adaptability of roof high position large-diameter directional borehole in Sanyuan Coal Mine and the influence of pore-forming pore size on gas extraction effect,two sets of roof high position large-diameter directional borehole with different pore sizes are tested and constructed on the experimental working face.In view of the problem of complex geological conditions,multiple fault structures,and many unstable strata in Sanyuan Coal Mine,composite drilling technique and broken and soft coal seam fixed-point grouting reinforcement technique are adopted in the experimental process to ensure that the roof high position large-diameter directional borehole is carried out to the designed hole depth.The experimental results show that the use of composite drilling technique and broken and soft strata fixed-point grouting reinforcement technique can effectively improve the borehole pore-forming property and pore-forming depth.In addition,a comparative analysis is conducted on the gas extraction data of two sets of roof high position large-diameter directional borehole with different pore sizes.The gas extraction mixing amount and extraction pure quantity of the borehole with a pore size of Ф 203 mm are 2.06 times and 1.82 times than that of the borehole with a pore size of Ф 153 mm,respectively,greatly enhancing the gas extraction capacity.
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