Crack initiation mechanism of pre-existing cracked granite

In order to explore the crack initiation mechanism of pre-existing cracked granite under uniaxial com-pression, the crack initiation angle, crack initiation stress and failure mode of cracked granite specimens with dif-ferent dip angles were analyzed by mechanical test and numerical calculation based on acoustic emission and surface strain field variation characteristics.The results show that the crack initiation is located at the tip of pre-existing crack, and the crack initiation angle increases monotonically with the increase of pre-existing crack angle.When the dip angle is 45°, the minimum crack initiation stress is 24.65 MPa.When 0°< β< 90°, the airfoil crack appears at the crack tip, and before loading to the peak strength, the anti-airfoil crack appears and leads to the instability failure of the specimen.When β=0°, the initiation crack is approximately parallel to the crack but does not continue to expand, and the specimen shows a compression shear failure mode.When β=90°, the initiation crack is approximately perpendicular to the crack and extends to the specimen.