Crack Growth in Rocks with Preexisting Narrow Flaws under Uniaxial Compression

Crack growth in rocks with preexisting flaws is of real concern for many rock engineering applications. The present paper considers the flaw that has a narrow gap that eventually gets closed on loading. Crack growth behavior leads to different failure modes, and corresponding strength characteristics were studied with respect to flaw angle. An experimental study was carried out with gypsum specimens replicating rock, that considered single and double flaws subjected to uniaxial compression. Crack growth and stress behaviors were analyzed and compared. The study was later extended to include numerical analyses using ABAQUS that adopted the extended finite element method with a cohesive zone model to capture crack growth behavior. The numerical model successfully mimicked wing crack propagation similar to the experimental results. The appearance of shear cracks and their growth upon loading was also predicted and crack initiation stress with respect to wing- and shear cracks was investigated. No significant differences were observed for single flaw specimens. However, in the case of multiple flaws with nonparallel configurations, the effect of shielding had a significant impact on coalescence behavior.