钻孔卸压防治冲击地压机理及影响因素分析

Analysis on mechanism and influencing factors of drilling pressure relief to prevent rock burst

为了防止煤体冲击地压,基于冲击地压应力控制理论,研究了钻孔卸压防治煤体冲击地压机理,推导了钻孔卸压区的边界方程,分析了煤体性质、钻孔直径及应力环境对钻孔卸压区分布的影响。研究结果表明,钻孔形成的弱化带破坏了煤体承载结构,导致顶板岩层与煤体界面内摩擦角与黏聚力大幅降低,大幅降低了巷帮浅部煤体应力,破坏了其发生冲击地压的应力条件;随着煤体黏聚力及内摩擦角的减小、钻孔与工作面距离的减小,钻孔卸压区增大且边界形状由椭圆形变为"X"形;随着钻孔直径的增大,卸压区增大但其边界形状不变。采用该方法进行煤体冲击地压防治钻孔布置参数设计,钻孔卸压使煤柱浅部煤体应力大幅下降,且应力峰值区域向煤柱深部转移,破坏了煤体发生冲击地压的应力条件,从而防治煤体冲击地压的发生,取得了良好的卸压效果。

In order to prevent rock burst of the coal body,based on the theory of rockburst stress control,the pressure relief mechanism of the boreholes was studied,the boundary equation of the borehole pressure relief area was derived,and the influence of coal properties,the diameter of borehole and stress environment on the distribution of borehole pressure relief zone was analyzed. The research results show that the weakened zone formed by drilling damages the bearing structure of the coal body,resulting in a significant decrease in the internal friction angle and cohesion at the interface between the roof rock and the coal body,greatly reduces the stress of the shallow coal mass in the roadway and destroys the stress conditions of rock burst. With the decrease of coal cohesion and internal friction angle and the decrease of the distance between drilling and working face,the pressure relief zone of the borehole increases and the boundary shape changes from an " oval" to an " X" shape. As the borehole diameter increases,the pressure relief zone increases but its boundary shape does not change. With this method,the design of drilling arrangement parameters for the prevention of coal rock burst is adopted. The pressure relief during drilling reduces the coal rock stress in the shallow part of the coal pillar,and the stress peak area is shifted to the deep part of the coal pillar,which destroyed the coal rock’s rock burst conditions and prevented the occurrence of coal rock pressure,and a good pressure relief effect was achieved.