煤层坚硬顶板爆破裂纹的扩展规律

Propagation Law of Blasting Crack in Hard Roof of Coal Seam

针对煤矿爆破中煤层坚硬顶板外加控制孔后爆破孔与控制孔之间存在裂纹扩展不佳的问题,以永宁煤矿10204巷道沿空留巷为工程背景,利用LS-DYNA动力显示有限元分析软件,研究了含有控制孔时侧压力系数u、不耦合系数r、控制孔与爆破孔间距L对坚硬顶板裂纹扩展的影响规律,并进行了现场验证。研究结果表明:随着侧压力系数的增大,孔间裂纹扩展形态呈现方向性的规律,裂纹数量增多、长度增长;随着不耦合系数的增大,峰值有效应力呈现先增大、后减小的趋势;r=1.67时,峰值有效应力最大,相对于其他不耦合系数时的峰值有效应力高出30%-40%。r=1.67时,若u≤1,L的最佳值为500 mm;若u>1,L的最佳值为650 mm。

In coal mine blasting, after the control hole is added to the hard roof of the coal seam, there is a pro-blem of poor crack propagation between the blasting hole and the control hole. In order to solve this problem, taking the gob-side retention of 10204 roadway of Yongning Coal Mine as the engineering background, effects of lateral pressure coefficient u, uncoupling coefficient r and distance between control hole and blasting hole L on crack propagation were studied by using LS-DYNA dynamic display finite element analysis software, and the field verification was carried out. The results show that with the increase of lateral pressure coefficient, the propagation pattern of inter hole crack presents a directional law, and the number and length of cracks increase. With the increase of the uncoupling coefficient, the peak effective stress firstly increases and then decreases. The peak effective stress reaches the maximum when the uncoupling coefficient is 1.67, which is 30%-40% higher than that of other uncoupling coefficients. When r is 1.67, if u≤1, the optimal value of L is 500 mm, and if u >1, the optimum value of L is 650 mm.