Extensive Propagation of 3D Wing Cracks Under Compression

Abstract

<p>The brittle failure of rock material is closely related to crack propagation and coalescence. Wing crack is the most common manifestation of crack propagation subject to compression. Previous studies proved that under uniaxial compression, 2D wing cracks were able to propagate extensively and split the rock specimen. In contrast, the propagation of 3D wing cracks was somehow restricted under uniaxial compression. However, under biaxial compression, even a small intermediate principal stress could trigger extensive 3D wing propagation. It remains elusive why extensive 3D wing propagation was so sensitive to intermediate principal stress. In this study, we develop a numerical model to simulate the propagation of 3D wing cracks under compression. The morphology of 3D wing cracks is correlated with axial compressive stress, which sheds light on the triggering mechanism of extensive 3D wing propagation. According to our interpretation, the reasons that extensive 3D wing propagation is sensitive to intermediate principal stress are twofold. (1) Intermediate principal stress is very effective to suppress lateral spalling, thus the specimen failure is solely attributed to the wing propagation. (2) Upon specimen failure under uniaxial compression, 3D wing cracks are in a critical state transitioning from stable to unstable propagation, and intermediate principal stress facilitates such transition. This study provides an in-depth understanding of the extensive 3D wing propagation under compression, which reconciles all elusive experimental phenomena in previous studies.<br></p>