Effect of interfacial angle on the mechanical behaviour and acoustic emission characteristics of coal–rock composite specimens

Abstract

This paper studies the mechanical and acoustic emission (AE) evolution characteristics of coal–rock composite specimens with different interfacial angles. Uniaxial compression tests with various interfacial angle are conducted, with acoustic emissions features being monitored. The test results show that both the peak stress and elastic modulus decrease linearly as the interfacial angle increases, whereas the peak strain does not exhibit a clear trend. Meanwhile, the failure mode changes from matrix splitting to interface slip failure. The AE evolution characteristics of a coal–rock composite specimen can be categorized into three stages: quiet period, active period and remission period. With an increase in interfacial angle, the duration of the quiet period gradually decreased. With the increase of stress, the RA value first stabilizes and then rises, while the AF value has a trend of periodic fluctuation and continuous decline. The decrease of AF and increase of RA can be used as precursors of instability in coal–rock composite specimens. The failure mechanism of the coal–rock composite structure is analyzed based on the mechanical model containing the structural plane, and the theoretical analysis result is consistent with the experimental result. The paper also discussed the field AE monitoring applications, and the results in this study can provide a reference for the study of rib failures when multi-layers are presented in the roadway.

Keywords

• Coal-rock composite structure
• Interface inclination
• Mechanical parameters
• Acoustic emission
• RA–AF value