Mechanical behaviours of granite containing two flaws under uniaxial increasing-amplitude fatigue loading conditions: An insight into fracture evolution analyses

摘要

This work aims to investigate the fracture evolution of granite containing two pre-existing flaws under uniaxial increasing-amplitude fatigue conditions using macroscopic stress strain descriptions and posttest three-dimensional (3D) computed tomography (CT) technique. The impacts of flaw arrangement (i.e., approach angle of 20°, 50° and 70°) on the stress strain responses, hysteresis loop shape, damage evolution and crack coalescence pattern at rock bridge segment were investigated. Results show that rock structure has an obvious impact on macroscopic stress strain responses, volumetric strain, dynamic elastic modulus and damping ratio. The sparse-dense pattern of hysteresis loop is different at each loading stage caused by the differential accumulative damage. The damping ratio increases and dynamic elastic modulus decreases with the increasing fatigue loading stage. Posttest 3D CT visualization reveals a most striking finding that crack coalescence is easy for rock having low approach angle, and complex crack network forms for rock having high approach angle.