Particle flow analysis of fracture characteristics of marble with a single hole

Based on uniaxial compression laboratory results, the failure process of marble with a single hole was simulated using the particle flow code PFC2D under uniaxial and biaxial compressions. The influence of the pre-existing hole shape, confining pressure and the rock heterogeneity on the mechanical properties of marble and the coalescence of cracks was analyzed. Numerical results show that compared to an intact marble specimen, the peak strength of a specimen containing a single hole reduces significantly, and the extent of reduction is related to the hole shape. The confining pressure has a significant effect on the mechanical properties of marble and the coalescence of cracks. The peak strength increases with the increase of confining pressure, while the peak deviator stress increases first and then decreases with the confining pressure increasing. Specimens containing circular holes exhibit X-type shear failure, while specimens containing rectangular or U-shaped holes exhibit diagonal shear failure. The mineral nodules in the rock specimen significantly affect the propagation of cracks leading to a change in the failure mode of marble specimen. Analysis results of the microscopic mechanisms show that the initiation and propagation of cracks around the hole is always accompanied by the release and transfer of stress from a concentrated zone. Three types of macroscopic cracks can be classified in specimen containing a single hole as hole surface spalling, tensile crack, and compressive shear crack.