Abstract
The objective of this article was to investigate the acoustic emission (AE) precursor information and crack propagation mechanism of brittle granite specimens containing a hole under uniaxial compression using AE and digital image correlation (DIC) techniques. The results show that the existence of the opening in the specimen leads to the degradation of the mechanical properties, and the stress-strain curve exhibits several stress drops. Each deformation stage of rock had different AE characteristics, so AE signals can be used to characterize the microscopic damage evolution of rock and predict the macroscopic failure process of the surrounding rock of the opening. The deformation field evolution process of the specimen containing an opening gradually develops from a uniform distribution to prominent local deformation, and the deformation of the local area near the opening is greater than that of other areas. The initiation of cracks begins around the opening, and the propagation of tensile cracks around the opening is primarily influenced by the nucleation and propagation in the strain localization area. The crack propagation evolution derived from DIC images can be combined with AE monitoring to accurately reveal the deformation and failure mechanism of the intact specimen containing an opening.
Highlights
E objective of this article was to investigate the acoustic emission (AE) precursor information and crack propagation mechanism of brittle granite specimens containing a hole under uniaxial compression using AE and digital image correlation (DIC) techniques. e results show that the existence of the opening in the specimen leads to the degradation of the mechanical properties, and the stress-strain curve exhibits several stress drops
Feng et al [17] believed that the failure strength of the cavity is a function of the inclination angle of the structure surface and the friction coefficient, and the critical inclination angle of the structure surface leading to the failure of the cavity largely depended on the friction coefficient. e above studies explored the failure modes and failure mechanisms of surrounding rock under different working conditions, which has greatly improved the understanding of underground engineering cavern disasters
To explore the physical and mechanical behavior of the surrounding rock under uniaxial compression, intact cuboid granite specimens with heights, widths, and thicknesses of 100 mm, 35 mm, and 35 mm, respectively, were first prepared. e aspect ratio of the sample was 2.86, which conformed to the test standard of the uniaxial loading test recommended by the International Society of Rock Mechanics (ISRM) [5] and can ensure that the central part of the specimen bore uniform stress during loading
Summary
After the completion of the intact specimen processing, circular openings with a diameter of 10 mm were fabricated by an improved high-pressure water jet cutting machine in the center of the intact granite samples. Two cameras were fixed on a tripod, and the camera position, focal length, and light source were adjusted according to the imaging quality of the sample on the computer so that the scattered spots on the sample surface could be identified, ensuring that the image on the specimen surface could be continuously and completely recorded during the whole test process. The AE signal source is generated in the sample After propagation, it is detected by the sensor installed on the specimen. When the uniaxial loading test started, AE equipment was started synchronously, and AE signals generated by specimen rupture during loading were obtained in real time. The AE and DIC measurements were performed synchronously to record the deformation evolution and AE signals corresponding to the stress-strain response of the samples
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