Acoustic emission characteristics of different brittle rocks and its application in brittleness evaluation

Rock brittleness is an essential factor affecting underground engineering disasters and energy extraction. A large number of cracks are generated during rock destruction, and many acoustic emission (AE) signals are accompanied. The propagation speed and modes of cracks in different brittle rocks differ during failure, and their AE signals also show differing characteristics. In this study, uniaxial compression experiments cooperating with AE monitoring on rock-like materials with different brittleness were conducted. We found that as the rock brittleness increased, the AE energy increased sharply during loading. During rock failure, the proportion of AE signals with lower RA (rise time/amplitude) and higher AF (average frequency) increased as rock brittleness increased. Based on the experimental results, the AE parameter ibE-value was proposed to evaluate the crack propagation state of the rocks. This ibE-value is also a parameter that determines the crack initiation point and residual stress point. Based on the variation characteristic of the ibE-value during the rock failure process and the first pressure drop after the peak of the rock, two evaluation criteria for rock brittleness were proposed. Compared with other brittleness evaluation criteria, these two evaluation criteria have better discrimination for different brittleness rocks, guiding human underground resource extraction and engineering disaster prevention.