On the fracture and energy characteristics of granite containing circular cavity under variable frequency-amplitude fatigue loads

Abstract

The cavities left after engineering construction obviously affect the stability of underground rock mass. Extensive studies have been devoted to investigate the mechanical behaviors of cavity-contained rock under static or impact stress paths, however, the damage process and energy dissipation characteristics were not well understood. The presented studies aim to reveal the volumetric deformation and energy dissipation characteristics of granite samples with different cavity orientations under unconventional cyclic loading conditions. The applied stress path is characterized with variable frequency-amplitude sinusoidal loads. Testing results show that the intersection between the maximum principal stress and cavity orientation affects the strength, deformation, energy, and failure modes. Crack damage evolution and hole collapse were revealed using strain rate and energy rate. It is found that the dissipated energy rate gives an early instability warning than the volumetric strain rate.A series of CT images of the failed rock give new insights into the mesoscopic mechanism of hole spalling and crack coalescence. A transition from tensile failure to shear failure was found as the cavity orientation increases with respect to the principal stress.