缺陷介质切槽爆破断裂行为的动焦散线实验

Dynamic caustic experiment on fracture behaviors of flawed material induced by pre-notched blasting

利用数字激光动态焦散线实验系统,对含缺陷介质在切槽爆破和普通炮孔爆破中爆生裂纹的断裂行为进行对比研究。结果表明,切槽爆破中沿切槽方向起裂的主裂纹比非切槽方向早10μs,有利于能量优先沿切槽方向释放;切槽方向主裂纹的起裂韧度为0.58 MN/m3/2,其裂纹扩展的平均速度为277 m/s,分别是普通爆破时主裂纹相应值的54%和86%;当切槽方向主裂纹与缺陷介质贯通后,为爆生气体提供了足够的膨胀空间,诱导爆生气体向预制裂纹两端释放,翼裂纹起裂以Ⅰ型拉伸破坏为主,并在裂纹扩展的60～250μs内,Ⅰ型动态应力强度因子保持在0.6～0.8MN/m3/2,形成了明显的平台,延缓了翼裂纹扩展速度的衰减,最终较普通炮孔翼裂纹扩展时间和扩展长度分别增加了22.7%和17.8%。

Using a digital laser dynamic caustics experimental system, the fracture behavior of blast- induced cracks in flawed materials under both ordinary borehole and pre-notched borehole were stud- ied. The results show that the main crack propagating along the pre-notched direction is 10 μs earlier than that along the non-notched direction, which attributes the blast energy release along with the pre-notched direction. The initiation toughness and average speed of the main crack in the pre-notched direction is 0. 58 MN/ma/2 and 277 m/s, respectively, corresponding to 54~//oo and 86% of the ordinary blasting. For the pre-notched blasting, The space is large enough for the detonation gas expansion, when the main crack goes through with the pre crack, and the detonation gas energy moving to the both ends of the pre-crack, leading mainly mode I type initiation fracture of the wing crack, with which its mode I dynamic stress intensity factor stays between 0.6 MN/m3/2 and 0.8 MN/m3/2 dur- ing 60--250 μs, which forms an obvious platform in the histories of mode I dynamic stress intensity factor, and the decrease rate of wing crack velocity are also delayed. Eventually, the duration time of the crack propagation and the crack length are increased by 22. 7% and 17.8%, respectively, com- pared with the ordinary borehole blasting.