类岩石裂纹压剪流变断裂与亚临界扩展实验及破坏机制

进行双轴压缩条件下类岩石裂纹的压剪流变断裂实验，采用双扭试件的常位移松弛法对类岩石材料进行亚临界裂纹扩展与断裂韧度试验。在实验室尺度上证实了类岩石裂纹流变断裂现象的存在，并且得到了翼形裂纹–翼形裂纹贯通、翼形裂纹–原生裂纹贯通和翼形裂纹–翼形裂纹–剪切裂纹贯通的 3 种流变断裂贯通模式。类岩石材料的流变断裂是一种稳定的裂纹扩展，其本质原因是类岩石裂纹的亚临界扩展。以黏弹性断裂力学、流变力学和能量准则为理论依据，推导以应力强度因子、翼形裂纹长度和时间为内变量的相应势函数，建立多种破坏机制的 压剪岩石裂纹的流变断裂 判据和计算模型。 利用 流变断裂 实验对计算模型进行验证，得出裂纹流变 贯通的 理论时间与实验时间较为吻合，当翼形裂纹的扩展方向与最大压应力方向偏离较大时实验结果与理论模型误差较大。提出的计算方法和理论判据为研究岩石裂纹的流变断裂的细观机理及岩体工程流变破坏的宏观机制提供了一个新而实用的研究手段。

Compressive-shear rheological fracture of rock-like cracks and subcritical crack propagation test and fracture mechanism

Based on the experiments of creep fracture of rock-like cracks under compressive-shear load and biaxial compression,a subcritical propagation fracture toughness test on rock-like materials is made by using the constant displacement load relaxation method of double torsion specimens.The presence of creep fracture is confirmed on a laboratory-scale,and three creep fracture coalescence patterns are obtained: wing crack to wing crack,wing crack to primary crack,and wing crack to wing crack to shear crack.The creep fracture of rock-like materials is a stable crack growth essentially due to the subcritical propagation of rock-like cracks.Subcritical propagation occurs in rock-like cracks.Based on viscoelastic fracture mechanics,rheologic mechanics and energy principles,the corresponding potential functions are deduced in which inner variables are stress intensity factor,wing crack length and time.The creep fracture criterion and computational model for various damage effects and rock cracks under compressive-shear load are established.Using the experiments of creep fracture to verify these computational models,the theoretical time agrees with the experimental one of creep coalescence.The error between the experimental results and theoretical models will be larger when the propagation direction of wing crack is far away from the direction of the maximum pressure stress.The proposed method and theoretical criterion will provide a new and practical tool for studying the microscopic mechanism of creep fracture of rock cracks and the macro-mechanism of creep fracture in rock engineering.