定向断裂控制爆破的空孔效应实验分析

Analysis of empty hole effect in directional fracture controlled blasting

采用新型数字激光动态焦散线实验系统,对爆炸荷载作用下空孔周围的动应力场分布及空孔对爆生主裂纹扩展行为的影响进行了研究。研究结果表明,在空孔周围强应力场的影响下,2条相向扩展的爆生主裂纹逐渐向空孔处偏转,并在空孔处贯通;空孔附近的主应力方向与炮孔连心线夹角基本稳定在约12°,增大空孔尺寸对空孔附近的主应力方向影响不明显;爆炸应力波与空孔相互作用,产生反射拉伸波,改变了主裂纹尖端的应力场,降低了主裂纹的扩展速度,且空孔直径越大,主裂纹的扩展速度越低;当爆生主裂纹扩展到空孔附近时,主裂纹尖端动态应力强度因子再次出现上升的趋势。

A new experimental system of digital laser dynamic caustics was used and the distribution of dynamic stress field around empty holes and the influence of empty holes upon the main cracks expanding under the blasting loading were studied.Experimental results show that two blast-induced main cracks,which were oppositely expanding,deflected gradually to empty hole under the strong stress and penetrated empty hole.The angle between the principal stress direction and the line of two blasting holes center near the empty hole kept about 12°,and the principal stress direction did not change with the size of empty holes increasing;the interaction between explosive stress waves and empty holes produced reflective stretching waves,changed the stress field at the main crack tips,reduced expanding velocity of the main crack.The larger the diameter of empty hole was,the lower the main crack propagation velocity was.When the blast-induced main cracks expanded to empty hole,the dynamic stress intensity factor at crack tips appeared to rise again.