Coal Geology & Exploration


The hard roof is a difficult problem in rock stratum control. The breaking and instability of high hard rock strata often induces strong coal pressure disasters, seriously threatening the safety production in coal mines. Hard roof control is one of the major problems in coal mine safety production. In response to the problems of large thickness, high hardness of the coal seam roof and its difficulty in collapse in Buertai Coal Mine in Shendong Mining Area, the hydraulic fracturing mechanism and technical advantages of directional long borehole segmented hydraulic fracturing are analyzed. The location of boreholes is determined based on the key layer theory. The effects of fracturing injection time and injection velocity on fracture propagation are analyzed and calculated by using the pseudo three-dimensional fracture model. The layout of the roof fracturing boreholes of 42108 working face in Buertai Coal Mine is determined, where three holes are arranged in parallel along the inclined direction of the working face. As the half length of the fracture is 41 m, the fracturing control area covers the whole working face. The practice shows that after the application of segmented hydraulic fracturing, the end cycle resistance of normal support in working face decreases by 3.33% in 42108 working face. During the period of cyclic pressure, the end cycle resistance of the support decreases by 6.81%. The dynamic load coefficient reduces by 10.88% on average. It weakens the strong coal pressure behavior of the mine, ensuring the mining safety of the working face.


long borehole directional drilling, hydraulic fracturing, hard roof weakening, mine pressure, Buertai Coal Mine of Shendong Coal Group




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