Study on the influence of length-diameter ratio on the mechanical characteristics of cracks at the end of linear charges
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摘要: 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５５ｍｍ，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／ １５）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Abstract: 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.
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