爆炸荷载作用下两平行裂纹对扩展中裂纹的影响规律

用实验和数值模拟方法，研究在爆炸载荷下岩体内部一对平行裂纹对扩展主裂纹的影响规律。实验中，采用带有中心装药孔及预制裂纹的砂岩圆盘试件，利用由示波器、超动态应变仪及裂纹扩展计所组成的测试系统，监测主裂纹扩展速度和扩展距离；数值模拟中，采用了AUTODYN软件进行，模拟了主裂纹及两平行裂纹的扩展规律，对岩石材料，采用线性状态方程及最大拉应力失效准则，并在两平行裂纹间设置相应的观测点记录应力曲线。通过实验与数值模拟分析，得到:爆炸载荷下，紧随冲击波后的稀疏波经过两平行裂纹面反射后变成压缩波，并在两平行裂纹间产生垂直于主裂纹扩展方向的压应力，对裂纹的扩展有压制、止裂作用；而且，这种压应力的大小与两平行裂纹的间距有关，进而导致了不同的止裂效果，影响裂纹的扩展速度及最终扩展长度。

Effect of two parallel cracks on main propagating cracks under blasting

There are many cracks inside the rock mass. In this paper, taking a pair of parallel cracks as an example, we studied the effect of two parallel cracks on the main crack’s propagation behavior and investigated the relationship of the main crack’s extended length with the two parallel cracks’ spacing, using experiment and numerical simulation. In our experiments, we used a circular sandstone specimen including a center hole charged with a detonator and pre-existing cracks and a test system consisting of an oscilloscope, an ultra-dynamic strain amplifier and crack propagation gauges (CPGs), and monitored the propagation velocity and length of the main crack. In our simulation we used the AUTODYN code to investigate the propagation behavior of the main crack and the two parallel cracks. We described the state of the rock material using the linear equation of state and the maximum tensile stress failure criteria, and designed some target points between the two parallel cracks to record the stress history. The experiments and numerical simulation show that the compressive stress perpendicular to the direction of the main crack occurs between the two parallel cracks under explosive loading; that, as a result of just following the shock waves and encountering the parallel crack surfaces, the rarefactional waves change into compressive waves, thus leading to the confinement of the propagating cracks; and that this compressive stress is related to the spacing between the two parallel cracks, and leads to differences in the main crack’s confinement, propagation velocity, and eventual propagation length.