基于GMTS准则的岩石复合型断裂机理研究

Investigation of Mixed Fracture Behaviors of Rock by the Generalized Maximum Circumferential Stress Criterion

使用国际岩石力学协会规定的半圆盘岩石试件,加工不同倾角的直裂纹试样,通过三点弯曲加载试验得到不同I-II复合比断裂的断裂韧性和初始断裂角.传统裂纹扩展准则忽视了常数项即T应力及更高阶项的影响,导致该扩展准则的理论预测结果存在较大缺陷,本文通过考虑常数项,建立广义最大周向应力准则(GMTS).在此基础上,分别采用传统的裂纹扩展准则和考虑T应力的裂纹扩展准则预测不同复合比裂纹的断裂韧性和初始扩展角,然后对比理论预测结果和实验结果.分析可得:常数项即T应力对断裂的临界应力强度因子和初始断裂角的影响是不可忽略的,且II型断裂占比较大时影响更大,广义最大周向应力准则预测值与实验测试结果之间的误差最小.

The fracture toughness and initial fracture angle of different I-II combined fracture were obtained by three-point bending test using the straight crack semi-disc rock specimens of different dip angles, processed following the standard of International Rock Mechanics Association. The traditional crack propagation criterion neglects the influence of the constant term, namely the T stress and the higher order. Therefore, the theoretical prediction results of traditional crack propagation criteria had an obvious defect, In this paper, the generalized maximum circumferential stress criterion （GMTS） is established by considering the constant term. The fracture toughness and initial fracture angle of different mode I-II fracture are predicted by the traditional crack propagation criterion and the generalized crack propagation criterion considering the T stress separately. The predicted results are compared with the experimental results. The analysis confirms that existence of T stress at the crack tip has a significant effect on mode I-II fracture for linear elastic materials, especially for mode II fracture; the generalized maximum circumferential stress criterion is more reliable compared to the traditional MTS criterion for predicting the fracture initiation angles and the fracture resistances for mixed mode fracture.