Microcracking behavior of three granites under mode I loading: Insights from acoustic emission

• Published in: Engineering geology 2020-12, Vol.278, p.105823, Article 105823
• Main Authors: Guo, Tian Yang, Wong, Louis Ngai Yuen
• Format: Article
• Language: English
• Subjects: Acoustic emission; Granite; Microcracking behavior; Mode I loading; Semi-circular bending test
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2020.105823

The mineralogy and texture of granite, which is a common host rock in geotechnical engineering practices such as tunneling, enhanced geothermal systems and nuclear waste disposal, significantly affect its microcracking behavior. However, the effects of these two attributes on the microcracking behavior of granite are not entirely understood. We study and compare the microcracking behavior of three granites, namely fine-grained (gf), medium-grained (gm), and coarse-grained (gc) granites, subjected to mode I loading using the semi-circular bending tests. The microcracking mechanisms are interpreted from the recorded acoustic emissions (AEs). Based on the AE signatures, three phases of microcracking processes, namely initial quiet phase, slow AE development phase, and rapid AE development phase, are identified. We find that the pre-existing microcracks affect the characteristics of the temporal evolution of microcracking behavior and associated energy release. The gm, which contains more pre-existing microcracks, has a relatively longer rapid AE development phase, during which the AE event rate and energy increase more gradually as compared with the gf and gc with fewer pre-existing microcracks. However, the grain size and mineralogy are found to have insignificant effects on the temporal evolution features of AE events and energy. The three granites show distinct AE event spatial evolution features, which results in different AE event distributions. The microcracking mechanisms derived from the AE results in laboratory study can shed light on interpreting the micro-seismic signals caused by the microcracking processes in geotechnical engineering practices with different granites as the host rocks •Mineralogy and texture affect the microcracking behavior of three granites.•Microcracking mechanisms studied by interpreting acoustic emission.•Pre-existing microcracks affect the temporal evolution feature of acoustic emission.•The acoustic emission results shed light on microseismicity interpretation.