The Radiation Energy of AE Sources with Different Tensile Angles and Implication for the Rock Failure Process

The AE energy radiated from rock microfractures is widely used to understand the rock failure process. However, the radiation energy of AE sources is usually inaccurately quantified because of imprecise knowledge of the radiation pattern associated with the tensile angle. Based on theoretical calculations, we quantify the radiation energy of the AE source more accurately by considering the influence of the tensile angle on the radiation pattern and then analyze the radiation energy evolution during the rock failure process. The energy radiation pattern and average energy radiation pattern coefficients of the P and S waves change significantly with the tensile angle. During the failure process of the granitic gneiss specimen, the radiation energy release of the rock specimen is characterized by a sudden intermittent increase in the time domain. The sudden increase is mainly due to the occurrence of large-energy AE sources rather than many low-energy AE sources in a short time. The main microfracture mechanism at the low stress level is shear compression; as the stress increases the main microfracture mechanism changes to shear. When the specimen is at failure, the shear microfractures account for > 70%.