冲击加载下的砂岩动态断裂全过程的实验和分析

采用圆孔内单边裂纹平台巴西圆盘(HSCFBD)新型试样在直径为100 mm的分离式霍普金森压杆上进行径向冲击加载,完成I型动态断裂实验,首次研究了砂岩的动态断裂全过程。实验表明,在低加载气压(0.16~0.17 MPa)驱动炮弹条件下,炮弹撞击速度为3.7~4.4 m/s,检测到试样的破裂历经裂纹的动态起裂、扩展和止裂3个阶段,止裂后到第2次起裂开始,裂纹停滞较长一段时间。采用裂纹扩展计测得裂纹起裂、扩展和止裂完整过程的瞬时时间,以此确定试样的动态起裂时刻、裂纹扩展速度和止裂时刻,并运用实验-数值-解析法分别得到砂岩的动态起裂韧度、扩展韧度和止裂韧度。从微观角度分析了动态起裂韧度和起裂时间的加载率效应。最后,初步讨论了试样内应力波反射对止裂的影响。

Complete dynamic fracture process of sandstone under impact loading:experiment and analysis

The authors are the first to study the complete dynamic fracture process in the mode-I rock dynamic fracture test by impacting diametrically the holed single cracked flattened Brazilian disc specimens of sandstone with large-diameter (100 mm) split Hopkinson pressure bar (SHPB).The dynamic crack initiation，propagation and arrest are detected successfully under the low air-pressure loading condition (0.16-0.17 MPa) for the projectile of SHPB，and the striking velocity of the projectile is 3.7-4.4 m/s.When the crack is arrested，the crack stays stationary for a comparatively long time before re-initiating.The dynamic initiation time，crack propagation velocity and dynamic arrest time were determined by the time signal measured by the crack propagation gauge.An experimental-numerical-analytical method was adopted to determine the dynamic initiation，propagation，and arrest toughness of sandstone.The effects of loading rate relating to the dynamic initiation toughness and initiation time were analyzed respectively from micro-scale perspective.