Mechanical and cracking behavior of granite specimens containing various inclusions

Holes and inclusions can significantly affect the mechanical properties and fracture modes of brittle rocks. This study adopted digital image correlation (DIC), grain-based model, elastic mechanics and complex function theory to investigate the influence of hole shape, filling material stiffness and contact surface properties on the mechanical responses and fracture behaviors of granite. The results demonstrated that the macrocracks included primary tensile cracks, secondary or remote cracks and sidewall slabbing fractures. The uniaxial compressive strength (UCS) and local stress drops during the damage and failure stages changed with the shape of the hole or inclusion. Filling material effectively mitigated the stress concentration around the hole, and enhanced the UCS and elastic modulus. The filling material significantly affected the failure modes of the samples, and the rigid material improved the structural integrity of the damaged samples. Moreover, the friction coefficient of the contact surface and the elastic modulus of the inclusion improved the UCS, but the strengthening effects were limited.