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.