Fracture behaviour of central-flawed rock plate under uniaxial compression

Fault fracture zone is a common engineering geological condition in mountain tunnel excavation, which often brings great difficulties to engineering construction. Thus, uniaxial compression experiments were carried out on the granite specimens with a central hole and hole edge flaws to investigate such engineering problems. And the crack initiation mechanism was studied by theoretical analysis and Extended Finite Element Methods (XFEM) simulation. The experimental results show that the mechanical parameters and crack types of the specimens distinctly vary with the flaw inclination. The mechanical properties of specimens such as strength are greatly weakened by the central hole and hole edge flaws compared with those of intact specimens, and the weakening effect decreases gradually with the increase of flaw inclination angle. When the inclination angle of flaw is small, the proportion of tensile cracks is high, resulting in tensile failure of specimens. While as the inclination angle of flaw increases, shear cracks gradually dominate, leading to shear failure in the specimen. In addition, the results of theoretical analysis and numerical simulation show that the wing crack initiation angle that appeared in the experiment are completely consistent with the theoretical and simulation results. And it is suggested by numerical results that the tensile stress at the flaw tip of specimens with flaw inclination angle of 15 degrees and 75 degrees is lower than that of other specimens, which may cause the absence of wing cracks.