Characteristics of microseism generated during rock shear failure under different normal stress conditions: an experimental study

• Published in: Arabian journal of geosciences Vol. 15; no. 12
• Main Authors: Su, Guoshao, Li, Lei, Jiang, Jianqing, Ren, Hongyu
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 2022; Springer Nature B.V
• Subjects: Acoustic emission; Amplitude; Amplitudes; Deformation; Deformation analysis; Dimensions; Distribution; Earth and Environmental Science; Earth science; Earth Sciences; Emission analysis; Failure; Fractal geometry; Fractals; Microseisms; Normal stress; Original Paper; Rock mechanics; Rocks; Shear strength; Shear tests; Stress; Waveforms; Quiet period; Direct shear test; Fractual; Normal stress; Microseism
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-022-10185-4

To investigate the characteristics of the acoustic emission and microseism occurring during rock shear failure, we conducted a series of direct shear tests on the cubic specimens under different normal stress conditions. First, the tested specimen shear strength, deformation characteristics, and crack during rock shear failure are investigated. Then, the waveform, fractal, and spectrum of microseism (MS) are analyzed. The deformation and stress characteristics of the tested specimen during the direct shear test are consistent with those obtained in the previous studies, indicating that the experimental results from our direct shear test are reasonable. In addition, a “quiet period” can be observed in the waveform of MS before the overall shear failure under low normal stress conditions for all the types of specimens. With the increase of normal stress, the relative length of the “quiet period” decreases, especially for the granite specimens, the “quiet period” will disappear. Otherwise, it can be obtained that before the overall fractal dimension exhibit a rapid increase. Furthermore, investigation on the frequency-amplitude distribution of MS indicates that high-amplitude MS signals occur during the rapid stress decreasing stage. Meanwhile, with the increases of the normal stress, more high-amplitude MS signals arise. The distribution of these high-amplitude MS signals changes from punctiform-shaped to bar-shaped and then clustered shape. It is concluded that the “quiet period” of MS waveform, the rapid increase of fractal dimension, and the appearance of high-amplitude MS before the overall shear failure can be taken as the precursor information to the overall shear failure.