Brittleness Effect on Acoustic Emission Characteristics of Rocks Based on a New Brittleness Evaluation Index

Brittleness has an important effect on the deformation and failure behavior of rocks. In this study, a brittleness evaluation index (B-p) based on the prepeak stress-strain curves of rock was proposed, and its effectiveness was verified by triaxial and uniaxial compression tests on different types of rocks. Based on the newly proposed index, the brittleness effect on the acoustic emission (AE) characteristics, such as the AE b-value, AE energy, average frequency (AF), and the ratio of the rise time to the peak amplitude (RA) of rocks under uniaxial loading was analyzed. The results show that the B-p has a linear negative correlation with the AE b-value. The stronger the brittleness of the rock, the smaller the AE b-value and the higher the ratio of macro to microcracks generated during rock failure. The brittleness effect on the variation law of the AE b-value is reflected during unstable crack propagation. In addition, rock brittleness affects the AF value but had no obvious influence on the RA value. The more brittle the rock is, the higher the proportion of tensile cracks in the fracture process. The research results could further enrich the evaluation system for rock brittleness and contribute to a better understanding of rock damage.