定向水力致裂对煤层顶板三向应力的影响研究

煤层顶板水力致裂是处理坚硬顶板和防治冲击地压的重要技术手段之一，为了研究水力致裂技术对煤层顶板三向应力的影响，通过现场开展煤层顶板定向水力致裂试验，采用光纤光栅三向应力传感器得到了致裂前后顶板岩层的三向应力。结果表明：水力致裂之后，监测断面处顶板岩层三个主应力均有所降低，最大降幅约为20%，而主应力方向变化很小|在工作面坐标系下，致裂部位处各应力分量的降幅受致裂面方位的影响。顶板水力致裂能够显著降低或者转移顶板岩层三向应力，对致裂部位具有良好的卸压效果。研究成果可为现场水力致裂钻孔布置提供参考，并可用于冲击地压防治研究。

Variation of three dimensional stress in rock after directional hydraulic fracture of coal seam roof

Hydraulic fracture of coal seam roof is one of the important means to deal with hard roof and prevent rockburst.In order to study the influence of hydraulic fracture on the three-dimensional stress of coal seam roof,a Fiber Bragg grating(FBG)sensor was adopted in the field test of directional hydraulic fracture of coal seam roof to monitor the three-dimensional stress in rock strata before and after hydraulic fracture.The results show that at the monitoring section the magnitude of three principle stress decreases after hydraulic fracture,and the biggest drop is about 20%;meanwhile the direction of three principle stress changes very little.In the working face coordinate system,the decline of every stress component at the fracture position is affected by the orientation of the fracture plane.Hydraulic fracture of coal seam roof significantly reduces or transfers the three-dimensional stress in roof strata,showing favorable pressure relief effect for fracturing position.The study can offer reference for the layout of hydraulic fracture boreholes,and the prevention and control of rockburst.