非贯通单节理岩体裂纹扩展方向研究

裂纹扩展方向的确定对分析岩桥破坏机制和岩体抗剪强度参数具有重要意义。首先以断裂力学观点推导了复杂应力条件下裂纹尖端应力分布函数的表达式，以节理岩体尖端的扩展裂纹可分为张拉裂纹和剪切裂纹为前提，基于Griffith破坏判据，提出了张拉裂纹扩展方向(张裂角)的计算公式；基于Mohr-Coulomb判据，提出了剪裂纹扩展方向(剪裂角)的计算公式。通过新判据与试验和其他判据的结果对比表明，该判据能准确判断张拉裂纹扩展方向，而剪裂角的扩展方向有待进一步试验验证。分析表明：在单向拉应力作用下，张裂纹扩展方向均有偏向于最大主应力方向的趋势，张裂纹与最大主应力夹角小于15°；双向拉应力作用下，随着微裂纹倾角变大，张裂纹有远离最大主应力方向的趋势；单轴压缩作用下，张裂角随裂纹倾角的增加而减小，而两者的和为先减小后增加。

Study on crack propagation direction of intermittent single jointed rock mass

It has a positive significance for further analysis of rock bridge failure mechanism and rock mass shear strength parameters to study crack propagation direction of intermittent jointed rock mass.The crack-tip stress field is derived from complex stress condition in the sight of fracture mechanics.Based on the existent rock bridge failure patterns, propagated crack of jointed rock mass is divided into two kind, tensile crack and shear crack.Then the formula of tensile angle θ_t is put forward according to Griffith failure criteria, and that of shear angle θ_c is also put forward according to Mohr-Coulomb failure criteria.Compared with other criteria and test, it shows that this criterion can accurately determine the direction of tensile crack growth, while the sheared angle needs further experimental verification.The result shows that the tensile crack propagation tends to bias towards the maximum principal stress direction under tensile stress and the angle between them is less than 15°.Under bidirectional tensile stress, tensile cracks tend to be far away from the maximum principal stress direction with larger crack angle.Under uniaxial compression, tensile angle decreases with the crack angle increasing, while their sum decreases and then increases.