近直立煤层顶底板爆破防冲方法数值模拟研究

Numerical simulation on roof and floor blasting rock burst prevention for nearly vertical coal seams

近直立煤层由于顶底板的挤压撬动作用,其冲击地压防治难度较大,本研究以乌东煤矿南采区为工程背景,进行了近直立煤层顶底板岩体爆破卸压防冲方法的研究。通过案例分析、数值模拟和现场验证等方法,分析了近直立煤层发生冲击地压期间采取的深孔爆破措施卸压防冲效果。尽管深孔爆破能够减少顶底板的压撬作用产生的动载,但对工作面近场围岩的弱化及静载的降低效果不佳。针对这些不足,提出了深浅孔爆破卸压防冲方法,结合深孔与浅孔爆破,既弱化了压撬作用导致的动载又有效弱化工作面围岩并降低静载集中,具体方法包括深浅孔交替爆破和深浅孔同时爆破。相比于单一深孔爆破,这两种方法都能进一步降低巷道围岩水平应力峰值。深浅孔同时爆破的防冲效果优于交替爆破,但工程成本更高。在乌东煤矿南采区应用了深浅孔交替爆破防冲。微震监测结果显示,相较于深孔爆破实施深浅孔爆破后,104 J以上大能量事件的发生率从9.3%降至0.2%,微震能量以“低频高能”转变为“高频低能”平稳释放,有效降低了冲击地压危险。研究成果可为近直立煤层冲击地压的防治工作提供重要支撑。

Due to roof and floor extrusion and prying of nearly vertical coal seams,the rock bursts prevention is challenging.Based on Wudong Coal Mine’s southern mining area,we investigate roof and floor rock body blasting and pressure relief methods for nearly vertical coal seams.In terms of case study,numerical simulation,and onsite validation,we analyze the effectiveness of deep hole blasting to release pressure during rock burst occurrences in nearly vertical coal seams.Although deep hole blasting reduces the dynamic loads caused by roof and floor extrusion and prying,it is less effective in weakening the nearby rock mass at the working face and reducing static loads.To solve this problem,we employ the combination of deep and shallow hole blasting to release pressure,which mitigates the dynamic loads from prying actions,and effectively weakens the working face rock mass as well as the concentration of static loads.The new technique includes deep and shallow hole alternative blasting and deep and shallow hole simultaneous blasting.Compared to single deep hole blasting,the new technique will further reduce the horizontal stress peak in surrounding rocks of the roadway.The simultaneous blasting is more efficient than alternative blasting,but it is at a higher engineering cost.In the southern mining area of Wudong Coal Mine,deep and shallow hole alternative blasting has been applied.Microseismic monitoring results indicate that,compared to deep hole blasting,the implementation of deep and shallow hole blasting will significantly reduce the occurrence of high-energy events(greater than 104 J)from 9.3%to 0.2%,and gently release the microseismic energy from“low-frequency high-energy”to“high-frequency low-energy,”which effectively mitigating the risk of rock bursts.These findings provide a significant support for preventing rock bursts in nearly vertical coal seams.