长径比对束状炮孔端部裂纹力学特征影响的研究

Study on the influence of length-diameter ratio on the mechanical characteristics of cracks at the end of linear charges

采用动态焦散线实验方法和损伤破坏数值模拟,对平面模型中束状炮孔端部爆生裂纹扩展规律和介质中拉/压损伤区进行了研究。实验结果表明,随着长径比的增大,爆生裂纹的扩展长度增大,扩展角度减小,用于产生端部裂纹的爆炸能量增多,有利于炮孔端部区域岩石破碎。当长径比为5/5时,裂纹扩展最大长度为55 mm,裂纹扩展角约为90°;长径比存在一定值,即当长径比增加到20(30/1.5)时,爆生裂纹扩展长度较大,裂纹扩展角减小到40°,爆生裂纹扩展速度和裂纹尖端应力强度因子整体为最大值;随着长径比的再次增加,扩展角不再变化。数值模拟结果与实验结果一致,炮孔柱部区域形成小面积的"椭圆状"压缩损伤区,而炮孔端部形成"X"形拉伸损伤区,容易形成爆生裂纹,拉伸损伤区半径约为压缩损伤区半径的5倍。

Dynamic caustic experimental method and numerical simulation method were used to study the crack propagation rules and the tension/compression damage zone at the end of boreholes in the planar model.The results show that the effect of different length-diameter ratios on the crack propagation was significant.As the length-diameter ratio increasing,the crack propagation lengths increased and the expansion angles decreased.When the length-diameter ratio was 5/5,the crack propagation angle was about 90°.When the length-diameter ratio increased to be 20(30/1.5),the crack propagation angles decreased to be 40°.As the length-diameter ratios increased again,the crack propagation angled didn’t change any more.The numerical results are in good agreement with the experimental results,and Numerical simulation shows that small area of compression damage area formed in the area of the column hole,and“X”type tensile damage zone formed at the end of the hole,which lead to the formation of explosive crack easily at the end of the borehole.The radius of the tensile damage zone was approximately 5 times the radius of the compression zone around the borehole.