Spectral Characteristics of Acoustic Emission in Loaded Coal Specimens for Failure Prediction

Resumo

Сhanges in acoustic emission spectra of coal samples from the Kuznetsk and Pechora Basins are experimentally studied in uniaxial and triaxial (Karman-type) compression tests. It is shown that the acoustic emission spectral patterns change considerably at the pre-failure stage in the samples under uniaxial compression: the amplitudes of low-frequency components grow while those of high frequencies reduce. Under the Karman-type compression, the amplitudes of low-frequency signals grow while the high-frequency amplitudes do not change much, because lateral hydrostatic pressure impedes opening of vertical fractures.