声发射特征在灰岩损伤识别及定量评估中的应用

The rock damage evolution is directly related to the safety control of major underground engineering. As the threshold stress in the process of rock deformation and failure, whether the characteristic stress can be accurately identified directly affects the effect of damage assessment. Based on the RMTTS stress test system and the MISTRAS acoustic emission test system, the related research on the crack stress identification and damage quantitative evaluation of limestone was carried out. The characteristics of acoustic emission (AE) signals corresponding to each stage of the stress-strain curve were analyzed by AE test under uniaxial compression of limestone, and the AE signals had a large increase in frequency and energy level when the crack propagation developed from stable stage to unstable stage. Based on the variation law of Felicity effect ratio FR during uniaxial cyclic loading of limestone, a crack damage stress identification method independent of strain measurement was proposed. The recognition results for 3 sets of limestone cores were in the range of 0.70${\sigma _{\rm{c}}} $～0.75$ {\sigma _{\rm{c}}}$, which was compared with the existing stress-strain method identification result 0.73${\sigma _{\rm{c}}} $ and verified the effectiveness of the method. The identification method of Felicity effect ensures the objectivity of the solution, and its identification range can be determined by the stress increment between cyclic loading. The damage evolution process of limestone was quantitatively evaluated by using the damage variable represented by AE energy. The results showed that the damage accumulated 17.4% in the stress range of 28.3% within the stable evolutionary interval of damage, while, the damage accumulated 80% within the stress range of 26.1% in the damage intensification evolution interval. The research achievements can provide technical supports for further understanding the damage evolution mechanism of rock in the engineering field.