不同药量的切缝药包双孔爆破裂纹扩展规律试验

 采用数字激光动态焦散线系统，研究有机玻璃板中不同药量的切缝药包双孔爆破主裂纹及分支裂纹的扩展规律。结果表明，切缝药包爆破主裂纹以I型拉伸断裂模式为主，爆破主裂纹难以穿过邻近炮孔的预制裂缝继续扩展；分支裂纹是预制裂缝尖端在爆破应力波衍射拉伸形成应力集中而萌生、起裂，相向分支裂纹分别扩展，最终呈“牵手状”贯通、止裂，分支裂纹贯通后扩展速度及动态应力强度因子急剧降低。对比不同药量模型试验结果发现，小药量炮孔相比大药量炮孔的爆破主裂纹、分支裂纹扩展速度及动态应力强度因子均较小，分支裂纹起裂时间较迟，且稳定扩展时间、扩展长度也较短，延长了分支裂纹贯通时间。相同药量两炮孔爆破主裂纹及分支裂纹断裂力学特征量近似相等，单炮孔的分支裂纹不贯通。试验研究为分析爆破裂纹扩展物理过程提供了参考。

Experimental study of crack propagation under two-hole slotted cartridge blasting with different amounts of charge#br#

The propagation behavior of both main cracks and branched cracks induced by two-hole slotted cartridge blasting with different amounts of charge masses in polymethyl methacrylate(PMMA) was studied by the digital laser dynamic caustics experimental system. The results showed that the main cracks induced by the slotted cartridge blasting grew mostly as mode I and showed the tensile fractures. These main cracks did not penetrate the prefabricated cracks close to the borehole to propagate further. The branched cracks were found initiated from the tips of the prefabricated cracks. The initiation and propagation of branched cracks were induced by the tensile stress concentration due to the blasting stress wave diffraction at the ends of prefabricated crack. The opposite branched cracks started to extend towards each other until their coalescence. The propagation velocity and the dynamic stress intensity factor(DSIF) of branched cracks decreased drastically after the coalescence. When the borehole was with less charge mass，the propagation velocity and DSIF of both the blast-induced main cracks and the branched cracks caused were lower，the branched cracks had longer initiation time and both the steady propagation time and the propagation length were shorter，which prolonged the time of coalescence. The dynamic fracture characteristics of main cracks and prefabricated cracks induced by the equally charged borehole were almost the same. The branched cracks induced by the singly charged borehole did not coalesce.