岩石裂纹亚临界扩展实验与压剪流变断裂模型

Rock cracks subcritical propagation test and compression-shear rheological fracture model

采用双扭试件的常位移松弛法对金川三矿区的大理岩、二辉橄榄岩和混合岩进行双扭试验,获得其裂纹扩展速率v与应力强度因子KI的关系及岩石断裂韧度,确定岩石亚临界门槛值K0。结合岩石压剪断裂理论和岩石亚临界裂纹扩展试验,建立压剪岩石裂纹翼形流变断裂扩展理论模型,提出翼形裂纹最终扩展长度由瞬时扩展长度和流变扩展长度组成。采用ANSYS断裂力学模块实现翼形裂纹尖端关键点随翼形裂纹扩展的自动生成,建立翼形裂纹流变扩展的数值分析模型。研究结果表明：采用常位移松弛法所测岩石的lg KI-lg v关系有很好的线性规律,3种岩石的K0/KIC在0.6-0.9之间;通过对算例进行理论分析和数值模拟,发现翼形裂纹流变断裂理论模型与数值分析结果很吻合。提出的岩石裂纹流变断裂理论为研究岩石裂纹流变扩展细观机理及岩体工程流变破坏的宏观机制提供了一个新的研究手段。

By adopting constant displacement load relaxation method of the double torsion specimens, the double torsion experiments of marble, lherzolite and migmatite in Jinchuan No.3 Mine were conducted to study the law of rock subcritical crack propagation. In addition, the relationship among crack growth rate v and stress intensity factor K1 as well as the value of rock fracture toughness were obtained, and the factor K0 of rock subcritical propagation was determined. The compression-shear crack of rock wing rheological fracture propagation theoretical model is established based on compression-shear fracture theory of rock and rock subcritical crack propagation experiments. It is also proposed that finally extended length of wing crack is combined with instantaneously extended length and rheologically extended length. By adopting the ANSYS fracture mechanical module, the key points of wing crack tips can be generated automatically as the wing crack propagation, and the wing crack theological extended numerical model can be established. The results show that when constant displacement load relaxation method is adopted, the relationship of lgK1-lg v is a good linear discipline and the K0/K1c values of three kinds of rock are between 0.6 and 0.9. Based on comparisons between theoretical analyzing and numerical simulation, it is discovered that there is a close correlation between the wing crack rheological fracture theoretical model and the numerical analysis result. The crack rheological fracture theory proposed has provided a new tool for studying microscopic mechanism of creep propagation of rock cracks and macro-mechanism of creep fracture in rock engineering.