基于声发射矩张量理论的混凝土裂纹机制反演

The locations, types and orientations of cracks on concrete specimens with bilateral openings during the shear failure process under uniaxial compressive loading are inversed to study the temporal and spatial evolution law of cracks based on the improved acoustic emission localization method and the moment tensor theory. The results of moment tensor analysis show that the growth of tensile cracks is dominant in the tensile damage zone, and the growth of shear cracks is dominant in the shear damage zone, which are consistent with the conditions of actual stress and damage in the specimen. This indicates that the moment tensor theory is a useful method to further study the mechanism of damage evolution in concrete, as it can be used for describing the distribution and migration of tensile stress and shear stress effectively. The results of waveform analysis show that the duration of acoustic emission (AE) signal corresponding to tensile crack is about 800 μs, and the frequency range is 7-500 kHz. The AE signals associated with mixed-mode crack and shear crack have frequency ranges from 7 kHz to 500 kHz and from 7 kHz to 250 kHz, respectively, and have higher duration of about 1 720 μs and 1 880 μs, respectively. The main reason is that the energy released by shear rupture is higher than that by tensile rupture, and the average frequency of shear wave released by shear rupture is lower than that of stress wave released by tensile rupture.