切缝药包微差爆破爆生裂纹扩展机理

为了研究切缝药包微差爆破孔间裂纹的动态力学行为特征,采用新型数字激光动态焦散线测试系统进行4组微差起爆实验。研究结果表明:随着延迟时间的增长先爆炮孔产生的裂纹长度依次增加,其受应力波作用前的扩展距离占总距离的比例依次增高,裂纹的贯通点逐渐靠近后爆炮孔,呈"牵手"状分布;应力波正压区的压缩作用和负压区的拉伸作用分别能够降低和提升对面裂纹的扩展速度v,延迟时间越长,裂纹扩展速度降低后的峰值越低,提升后的峰值越高,爆炸应力波在对面裂纹尖端产生的压应力场会降低其动态应力强度因子KdI,延迟时间越长,峰值越小;裂纹相遇时,扩展速度v和动态应力强度因子KdI都呈现增大趋势,且相遇越早,速度峰值越大;当微差时间满足一定条件时,先爆炮孔产生的应力波在后爆炮孔孔壁附近形成拉伸应力场,有利于裂纹萌生。

Mechanism of explosive crack propagation with slotted cartridge millisecond blasting

The new testing system of digital laser dynamic caustics was developed to carry out four groups of millisecond blasting experiments for studing the dynamic mechanical behavior of explosive crack propagation with slotted cartridge millisecond blasting.The results show that the longer the delay initiation time,the farther the propagation distance of crack generated by the first detonating borehole,the higher the ratio of crack propagation distance before action of stress wave to the total distance,and the penetration point of two cracks gradually closes to the later detonating borehole,into a “hand in hand” shape distribution;the compression effect from the positive pressure zone of stress wave and the stretching effect from negative pressure zone of stress wave can decrease and increase the velocity of opposite crack propagation,respectively.The longer the delay initiation time,the lower the peak value of decreased velocity of crack propagation and the higher the peak value of increased velocity of crack propagation.The compression stress field of the explosive stress wave at the opposite crack tip can decreases mode I dynamic stress intensity factor,and the longer the delay initiation time,the smaller its peak value;both the velocity of crack propagation and the dynamic stress intensity factor increase suddenlly when two cracks meet.The earlier the encounter,the higher the peak value of velocity;when delay initiation time satisfies certain conditions,the stress wave generated by the first detonating borehole forms a tensile stress field near the borehole wall of the later detonating borehole,which is favorable to the initiation of crack.