综掘工作面过硬岩正断层爆破方式优选实验研究

Experimental study on optimum blasting method of crossing hard rock normal fault in fully mechanized mining face

针对综掘正断层区域爆破弱化硬岩导致煤岩失稳的问题,采用室内模型实验,对比总结聚能爆破和普通爆破的裂纹扩展模式、应力演化规律及煤岩破坏特征,利用实验结果指导工程现场。研究结果表明:普通爆破中爆破孔与正断层上盘煤层连线区域内形成的裂纹密集区是煤与瓦斯突出危险区域,试块模型各检测面超声波平均波速下降26%,煤岩体破坏严重。聚能爆破中聚能方向1^(#)测点最大压应力峰值是普通爆破的1.72倍,是非聚能方向4^(#)测点的2.84倍,聚能方向裂纹定向扩展,试块模型各检测面超声波平均波速下降4.12%,聚能爆破在定向破岩的同时可以有效保护正断层构造区域煤岩体不受破坏。优选聚能爆破技术在正断层综掘现场的应用表明,使用聚能爆破技术弱化断层硬岩有效保证了巷道周边煤层及围岩的完整性,避免了构造区域爆破扰动煤岩诱发瓦斯突出灾害的问题,使巷道掘进得以安全高效进行。

Aiming at the problem of coal rock instability caused by blasting weakening hard rock in normal fault zone of fully mechanized excavation,the similar blasting simulation test was carried out in the laboratory.The crack propagation mode,stress evolution law and coal rock failure characteristics of cumulative blasting and ordinary blasting were compared and summarized,and the test results were used to guide the engineering practice.The results show that the crack-intensive area formed in the connection area between the blasting hole and the coal seam on the upper panel of the normal fault is a dangerous area for coal and gas outburst.The average ultrasonic wave velocity of each detection surface of the test block model decreases by 26%,and the coal and rock mass is seriously damaged.In the cumulative blasting,the maximum compressive stress peak value of measuring point 1^(#)in the direction of energy accumulation is 1.72 times that of the ordinary blasting,and 2.84 times that of measuring point 4^(#)in the direction of non-energy accumulation.The cracks in the direction of energy accumulation expand directionally,and the average ultrasonic wave velocity of each detection surface of the test block model decreases by 4.12%.The cumulative blasting can effectively protect the coal and rock mass in the normal fault structure area from damage while directional rock breaking.The field application of preferred cumulative blasting technology in normal fault zone shows that the use of cumulative blasting technology to weaken fault hard rock effectively could ensure the integrity of coal seam and surrounding rock around the roadway,avoid the problem of gas outburst disaster caused by blasting disturbance of coal and rock in structural area,and make roadway excavation safe and efficient.