硬厚致灾岩层预裂爆破防冲参数优化及工程实践

Optimisation of anti⁃impact parameters and engineering practice of pre⁃split blasting for hard⁃thick disastrous rock strata

针对彬长矿区某矿硬厚粗粒砂岩致灾层预裂爆破效果不佳的问题,采用数据分析、数值模拟及工程试验等方法研究了预裂爆破关键参数,模拟分析了岩石抗拉强度、炸药装药密度、不耦合系数及爆破孔间距对预裂爆破效果的影响,优化了针对粗粒砂岩层的爆破参数。结果表明:开展预裂爆破工程时,应当考虑爆破参数与岩层抗拉强度相适应,避免炸药能量浪费在破碎区、削弱裂隙区裂纹扩展尺度;较小炸药装药密度下,增大装药密度明显促进爆破裂纹扩展,而较大装药密度下促进作用不明显,易导致破碎区范围明显增大,浪费炸药能量;不耦合系数的最佳区间为1.42~1.58,此区间外裂纹扩展尺度较小,爆破效果不理想;增大炮孔间距,孔间裂纹贯通趋势减弱,爆破效果变差,较优的炮孔间距为10 m。优化了粗粒砂岩层的爆破参数,现场试验后工作面来压步距与支架阻力明显降低,大能量微震事件总能量与事件数占比显著降低,卸压效果较好。研究结果可为硬厚岩层预裂爆破参数设计提供参考。

In response to the poor pre⁃split blasting effect of hard⁃thick disastrous rock strata in Binchang mining area,the key parameters of pre⁃split blasting are studied by data analysis,numerical simulation and engineering tests.The effects of rock tensile strength,explosive charge density,uncoupling coefficient and blasting hole spacing on pre⁃split blasting effect are simulated and analyzed,and the optimal blasting parameters for coarse⁃grained sandstone layer are obtained.The results show that the choice of blasting parameters during pre⁃split needs to be compatible with the tensile strength of the rock formation,to avoid wasting explosive energy in the fracture zone and weakening the scale of crack ex⁃pansion in the fracture zone.In the case of small explosive charge density,increasing the charge density obviously promotes the propagation of blasting crack,while in the case of large explosive density,the promoting effect is not obvious,which is easy to lead to the obvious increase of the range of crushing zone and waste the explosive energy.The optimal interval of the decoupling coefficient is 1.42-1.58,beyond which the crack expansion scale is small and the blasting effect is not ideal.Increasing the hole spacing reduces the tendency for inter⁃hole fracture penetration and makes blasting less effective,with a better hole spacing of 10 m.blasting optimisation parameters are determined for coarse sandstone,and the pressure step and support resistance of the working face are significantly reduced after the field test,with a significant reduction in the total energy and number of events of large energy microseismic events and a better pressure relief effect.The results can be used as a reference for the design of pre⁃split blasting parameters for hard⁃thick rock strata.