低渗煤层预裂爆破裂纹扩展规律数值模拟研究

Numerical Simulation on Crack Propagation Law of Pre-splitting Explosion in Lowly Permeable Coal Seam

针对低透气性煤层实施深孔预裂爆破过程中爆炸应力波和爆生气体作用下裂纹扩展范围和规律现场难以测量的问题,采用理论和数值模拟相结合的方法,对低渗透煤层进行单孔和双孔预裂爆破数值模拟,得到了不同爆破参数下应力、压力和单位质量塑性功等物理量动态变化规律和裂纹扩展范围,分析了深孔预裂爆破裂纹扩展规律和煤体在高温高压爆生气体及应力波作用下破坏区域的演化规律。炸药在煤体内爆炸的瞬间,产生的压力远大于煤体所能承受的动态抗压强度,煤体被破坏形成爆破空腔,当爆炸冲击波在孔壁上产生初始径向裂隙后,爆生气体楔入裂隙中使其继续扩展,在煤体内形成粉碎区、裂隙区、震动区,揭示了煤层在爆炸应力波和爆生气体作用下的损伤断裂机理。

The crack propagation behavior under the explosion stress waves and detonation gas was difficult to measure in deep-hole pre-splitting explosion in lowly permeable coal. The single blast hole and double blast holes pre-splitting explosion lowly permeable coal seam were studied by numerical simulation. The laws of different blasting parameters such as stress, pressure and total plastic work performed on a cell material at any time process variation and the crack propagation range were obtained. The crack propagation behavior of deep-hole pre-splitting explosion and the evolution law of the damage region of coal body under detonation gas and stress wave at high temperature and pressure were discussed. When the explosion was in coal body, the pressure would be far greater than the coal body compressive strength, then the coal body was destroyed and the blast cavity was formed. When the shock wave was generated in the wall of the hole after the initial radial cracks, the detonation gas would cause it expand into the fis- sure ,finally the pulverized zone,fractured zone and vibration zone were formed in coal body. The study helped to dis- close the coal damage fracture behavior under the explosion stress wave and detonating, and further to determine the reasonable blasting scheme and the blasting parameters in the coal seam pre-splitting explosion technology.