Determination of the stress field and crack initiation angle of an open flaw tip under uniaxial compression

In the uniaxial compression test of rock containing pre-existing flaws, the flaws are generally open, and the corresponding theoretical calculations are mostly based on the closed flaws. The suitable theoretical solution is needed for the crack initiation and extension of open flaws (Flaw: Prefabricated, inherent defects. Crack: Defects generated during the loading process). In this paper, first, the corresponding stress field formulae under compression are established by comparing and analyzing the stress field at the flaw tip under tensile condition. Then, ANSYS is used to simulate and confirm the stress field at the flaw tip under compression and shear conditions. Thus, the difference between the open flaw and the closed one is explained, and the stress field formulae of the open flaw tip under compression are determined without considering the flaw thickness. Second, based on the determined stress field formulae at the flaw tip, the relationship between the crack initiation angle of the open flaw tip and the inclination angle of the prefabricated flaw is derived. Finally, laboratory test and PFC simulation are conducted to verify the resulting crack initiation angle formulae. The experimental and simulation results are basically consistent with the theoretical formula.