Brittle Failure Modes and Mechanisms in Foliated Rock Under Uniaxial Compression: Laboratory Testing and Particle Flow Modeling

Uniaxial compression tests were conducted on quartz mica schist in a laboratory to study the brittle failure modes of foliated rocks. By focusing on the crack evolution pattern, the failure mechanisms of foliated rocks were investigated by numerical tests based on particle discrete element theory. Furthermore, the effect of fabric on the mechanical anisotropy of foliated rocks was explored. The results indicated that the failure of foliated rocks subjected to uniaxial compression is heavily controlled by the rock fabric, exhibiting complex modes depending on the loading direction, including axial tensile fracture, oblique shear fracture, conical shear fracture, slip shear failure and splitting failure. Cracks initiated in the compressed rocks are induced from the contact surfaces of granular and flaky minerals and from the tips of flaky minerals. The crack initiation of foliated rocks, attributed to the concentration of tensile stress within the rock, responds to the loading direction in terms of the induced mechanism. When α = 90°, 45° and 0°, crack initiation depends on the differences in the mechanical properties of different minerals, the slipping of flaky minerals, and the kinking of flaky minerals, respectively. The formation of primary fracture planes results from tension crack coalescence + shear crack connection (α = 90°), shear crack or tension‒shear composite crack connection (α = 45°), and tension crack coalescence (α = 0°). As the orientation degree of flaky minerals decreases, the failure mode experiences a gradual decrease in sensitivity to the loading direction, and the curve of strength variation with orientation angle changes from U-shaped to shoulder-shaped or wave-shaped, accompanied by a decreasing anisotropy degree of rock strength.