Directional hydraulic fracturing of roof for control large deformation of dynamic pressure entry heading adjacent advancing coal face

• 1、School of Mines,China University of Mining & Technology, Xuzhou 221116
• 2、Key Laboratory of Deep Coal Resource Mining, Ministry of Education of China,Xuzhou 221116

Abstract：When the longwall mining is utilized in coal mine, due to some difficulties in the succeed of mining and tunneling or double entry layout, it often occurs that the entry of the adjacent working face has been tunneled before the working face is mined or the entry of the adjacent working face is being tunneled when the working face is being mined. Influenced by the dynamic pressure of front abutment pressure and lateral abutment pressure, large deformation of the surrounding rock occurs in a range of advancing working face in the meet mining entry. To control large deformation of dynamic pressure entry heading advancing coal face, drill holes in entry or in high drainage roadway to certain rock layer over adjacent working face and conduct hydraulic fracturing. Hydraulic cutting seam or slotting in bottom of drill-hole are also adopted in advance to guide the directional extension of hydraulic fracture, cut off the hard roof above coal-pillar directionally, break the roof's integrity and wet and soften coal or rock layer. Combined effects of directional fracturing and wetting and softening make the roof cave in time, decrease front abutment pressure and lateral abutment pressure in entry heading advancing coal face, transfer the stress, decrease the influence of dynamic pressure and improve the distribution of abutment pressure in coal-pillar. The in-situ test at Majialiang coal mine indicates that the cracks propagation length of one borehole is not less than 15 m; the roof control range is not less than 30 m. After hydraulic fracturing, the severe deformation range of entry heading adjacent advancing coal face is reduced by 45 m, the average floor heave is reduced by 70%, the average convergence of the entry's two sides is reduced by 65%. Directional hydraulic fracturing of hard roof better controls the large deformation of dynamic pressure entry heading adjacent advancing coal face and guarantees the mine's safety production and the working faces' normal succeed.

Keywords： Mining engeneering entry heading adjacent advancing coal face dynamic pressure entry large deformation hydraulic fracture stress transfer