煤岩体双孔爆破应力波及裂纹扩展叠加效应分析

Research of stress wave and crack propagation superposition effect of double-hole blasting in coal and rock mass

针对煤岩体松动爆破施工中炮孔间距和爆破方案选择的问题,根据岩石动力学及爆破理论计算了双孔爆破裂隙区贯通的炮眼间距,并采用LS-DYNA分析了双孔爆破应力波及裂纹扩展叠加效应对炮孔间距和爆破方案的影响。结果表明:双孔同时爆破,炮孔间距3.4 m(单孔爆破裂纹半径的2倍)时,炮孔间的裂隙区不能全部贯通,炮孔间距2.5 m时,炮孔间的裂隙区才能够全部贯通;微差爆破,炮孔间距3.4 m时,由于先爆炮孔周围裂隙区的裂纹在后爆炮孔应力波的叠加作用下发生明显的二次扩展,炮孔间的裂隙区能够基本贯通,而炮孔间距3.0 m时,炮孔间的裂隙区能够全部贯通并覆盖钻孔间全范围;现场采掘面进行松动爆破时,炮孔间距一般应小于单孔爆破裂纹半径的2倍(炮孔同时爆破约取单孔估算炮孔间距的70%,微差爆破约取单孔估算炮孔间距的90%),才能保证松动爆破效果;微差爆破与炮孔同时爆破相比,不但能保证爆破效果,而且还可以减少炮孔数量和爆破材料用量,是优先选择的爆破方案。

Aiming at the problems of hole spacing and blasting scheme selection in coal rock loosening blasting construction,the distance between the holes in the fracture zone of the double hole blasting is calculated based on rock dynamics and blasting theory,and LS-DYNA is used to analyze the influence of stress wave and crack propagation superposition effect on the spacing of blasting holes and blasting plan in double hole blasting.The research results indicate that:when two holes blasting simultaneously and the spacing between the holes is 3.4 m(twice the crack radius of a single hole blasting),the crack areas between the holes cannot be fully connected;when the hole spacing is 2.5 m,the fracture zone between the holes can be fully penetrated;and in millisecond blasting,when the spacing between the blast holes is 3.4 m,due to the obvious secondary expansion of cracks in the crack area around the first blast holes under the superposition of stress waves in the later blast holes,the crack areas between the blast holes can be basically connected.However,when the spacing between the blast holes is 3.0 m,the crack areas between the blast holes can be fully connected and cover the entire range of the drill holes.When loosening blasting is carried out on the excavation surface on site,the spacing between blast holes should generally be less than twice the crack radius of a single hole blasting(approximately 70% of the estimated spacing between blast holes for simultaneous blasting and 90% of the estimated spacing between blast holes for millisecond blasting)to ensure the effectiveness of loosening blasting.Compared with simultaneous blasting,millisecond blasting can not only guarantee the blasting effect,but also reduce the number of holes and the amount of blasting materials,so it is the preferred blasting scheme.