基于最大周向应变的岩石复合型断裂准则解析与验证

Analysis and verification of rock mixed mode fracture criterion based on maximum circumferential strain

为提高对线弹性材料复合型裂纹扩展预测的精确性,弥补常用的最大周向应力准则未考虑材料泊松比且无法区分平面应力与平面应变的缺陷,从应变角度出发,并考虑了非奇异应力项(T应力)在脆性断裂中的作用,建立了基于最大拉应变准则的线弹性材料裂纹扩展判别准则,研究T应力和泊松比对岩石裂纹扩展的影响。结果表明:裂纹倾角β<45°时,裂纹起裂角预测结果随无量纲特征距离α的增大而增大;裂纹倾角β>45°时,裂纹起裂角预测结果随α的增大而减小;考虑T应力的最大周向应变准则起裂角预测值与试验数据更加吻合,裂纹扩展受T应力和应力强度因子的共同作用,T应力和无量纲特征参数均对岩石裂纹断裂特性具有很大影响,采用考虑T应力的最大周向应变准则判断岩石裂纹的断裂特征能够弥补基于应力的裂纹扩展判别准则的不足。

In order to improve the accuracy of the prediction of composite crack growth in linear elastic materials,and overcomes the defects that the commonly used maximal circumferential stress criterion does not consider material Poisson’s ratio and cannot distinguish plane stress and plane strain,starting from the strain point of view,and considering the role of T stress in brittle fracture,a linear elastic material crack propagation criterion based on the maximum tensile strain criterion was established and applied to study the influence of T stress and Poisson’s ratio on rock crack propagation.The results show that when the crack inclination angleβ<45°,the prediction result of the crack initiation angle increases with the increase ofα;whenβ>45°,the prediction result of the crack initiation angle decreases with the increase ofα;The maximum circumferential strain criterion considering the T stress is more consistent with the experimental data,and the crack propagation is affected by the combined action of the T stress and the stress intensity factor.The combination of the strength factors,T stress and Poisson’s ratio have great influence on the fracture characteristics of rock cracks.The maximum circumferential strain criterion considering T stress,to judge the fracture characteristics of rock cracks,can make up for the insufficiency of the criterion of crack propagation based on stress.