Acoustic emission spectrum characteristics and localization evolution mechanism of coal and coal gangue specimen failure

The mechanical experiments and acoustic emission (AE) experiments of unconfined compression strength (UCS) of coal and coal gangue specimens are carried out to investigate the mechanical characteristics and AE waveform spectrum and localization evolution characteristics of coal and coal gangue specimens. The phase distribution characteristics of the RA-AF values of AE signals are used to characterize the different rupture modes of coal and coal gangue specimens. The fast Fourier transform (FFT) method is used to obtain two-dimensional spectral maps of AE signals, extract their main frequencies, and analyze the spectral characteristics of the phase failure of coal specimens. Further, AE signal localization events are selected to study the localization evolution information of coal and coal gangue specimens in the process of phase failure. The experimental results show that the coal gangue specimens have high strength and brittle damage; the largest transverse volume expansion is in the coal specimens, and the coal gangue specimens show the characteristics of high AF and low RA in the 0-0.6o -f stage, while the coal specimens show the characteristics of high AF and low RA in the 0-0.4o -f stage. The coal gangue specimen, in the initial period of loading, has a small number of AE events, but the AE aggregation phenomenon occurs. The AE events of coal gangue specimens are obviously distributed along the fracture surface and present aggregation in space, while the AE events of coal specimens show a scattered state.