EXPERIMENTAL STUDY ON THE INFLUENCE OF AXIAL AND CIRCUMFERENTIAL DEFORMATION LOADING CONTROL MODES ON THE MECHANICAL AND ACOUSTIC EMISSION CHARACTERISTICS OF GRANITE

The loading control mode is one of the key factors affecting the mechanical properties of rocks. In this study, two loading control modes—axial deformation control and circumferential deformation control—were used to conduct uniaxial compression tests on granite specimens at a deformation rate of 0.005·s^-1. The effects of different loading control modes on the mechanical and acoustic emission(AE)characteristics of granite were explored. The influence of these modes on peak strength, stress and strain thresholds, energy evolution, and AE characteristics of granite was analyzed. The results show that the peak strength, crack damage stress, and crack initiation stress of specimens under axial deformation control are 12.8%, 15.1%, and 13.1% higher, respectively, compared to those under circumferential deformation control. The peak axial strain, axial damage strain, and crack initiation axial strain are 12.5%, 14.3%, and 15.2% larger, respectively, while the peak circumferential strain and crack initiation circumferential strain are 24.2% and 16.7% smaller, respectively. The total energy is 23.9% higher, and the energy storage capacity(Re) is 2.6% greater under axial deformation control. Furthermore, the cumulative count and cumulative energy of acoustic emissions are 48.8% and 106.1% higher, respectively, and the AE b-value is 14.1% larger. Analysis of the AE AF-RA value indicates that the two loading control modes do not significantly affect the fracture type of the samples. These research findings are of great significance for further understanding the fracture mechanism of brittle rocks.