Mechanical characteristics and energy evolution of rock with circular hole defects

In this paper, the uniaxial compression damage characteristics of specimens are analyzed containing holes using PFC2D. In addition, the crack propagation, stress distribution and energy development characteristics of the specimens were systematically discussed. The findings indicate that the strength parameters of various specimens drop initially and then increase with increasing center point connecting angle, in comparison to intact rock. The most significant reduction in strength parameters is observed at a center point connecting angle of 45°. The stress concentration around the holes occurs prior to crack initiation and vanishes upon specimen failure. The number of cracks in the specimens is small and the propagation length is short before touching the peak value, while the cracks expand rapidly in a short period of time after the stress touches the peak value, and the crack development rules in the two stages are quite different. With increasing center point connecting angle, the pre-peak energy and total energy drop first and then increase. After touching the peak value, the specimen is dominated by energy release and the ability to absorb energy is weakened. In the case of center point connecting angle of 45°, the specimen has the largest energy difference coefficient and the worst ability to resist damage. The damage behavior can be composed of no damage, initial damage and accelerated damage take into account the damage change rules of the specimens.