冲击荷载下岩石裂纹动态扩展全过程演化规律研究

为研究岩石裂纹全过程扩展规律及扩展行为中的定区域止裂问题,提出修正侧开半孔板(improved single cleavage semi-circle specimen,ISCSC)构型构件。通过大直径分离式霍普金森压杆试验系统进行冲击试验,使用裂纹扩展计测试系统测定了裂纹扩展速度,同时引入拉伸断裂软化损伤破坏模型进行数值模拟,通过试验–数值法,深入分析动载荷下岩石裂纹全过程扩展演化行为及双空心孔对于裂纹扩展的影响。结果显示,ISCSC构型实现了裂纹扩展中的定区域止裂,可以精准预测止裂区域;预制双空心孔的构型分布对裂纹扩展行为影响巨大,裂纹扩展速度受到明显抑制;裂纹扩展至双孔中心连线区域时,裂纹尖端拉应力场与双孔形成的叠加应力场相互作用,导致主裂纹扩展速度急剧降低,甚至出现止裂现象;裂纹扩展至叠加场时,极易受到物质不均匀性影响,产生偏折或分叉;同时,数值计算的结果和试验吻合,验证ISCSC构型用于研究裂纹起裂、扩展及止裂全过程演化行为的有效性。

Study on evolution law of rock crack dynamic propagation in complete process under impact loading

In order to study the mechanism of crack propagation in complete process and crack arrest behavior in set area between two holes,an ISCSC(improved single cleavage semi-circle specimen) configuration specimen was proposed. By using split Hopkinson pressure bar,the impact experiment was conducted with the crack propagation velocity detected by the crack propagation gauge. Meanwhile,the damage failure model combining principal stress failure criteria with crack softening failure criteria was introduced in the numerical simulation. With Experiment-Numerical method,the evolution law of rock crack dynamic propagation in complete process was investigated elaborately and the effect of two empty holes on crack propagation behavior was sophisticated demonstrated. The results show that the ISCSC configuration specimen could realize the crack arrested in set area and that the arrest zone can be predicted accurately. Two empty holes have huge influence on the behavior of crack propagation,restraining crack propagation velocity obviously. The interaction of the superimposed stress field between two empty holes and the tensile stress field of the crack tip could slow down the crack propagation speed sharply and even cause arrest when the running crack rushes into the set area between two holes. When the running crack goes across the set area between two holes,the crack propagation behavior could be influenced by inhomogeneity of material easier than before,which could cause crack deflecting and branching. It is also shown that numerical simulation outputs agree well with the results of experiment,confirming that ISCSC configuration specimen has great ability to be applied in researching the behavior of crack propagation in complete process.