COAL DAMAGE EVOLUTION UNDER COMPRESSION-SHEAR LOADING: INSIGHTS FROM ACOUSTIC EMISSION DATA

In the compression-shear loading experiment of coal samples, the relationship between acoustic emission signals and sample failure process was analyzed from the time domain characteristics, frequency spectrum characteristics, and fracture component characteristics of acoustic emission signals. The experimental results show that during the compression-shear failure process of coal samples, tensile fracture occurs at the inflection point of the stress curve, while shear fracture occurs at multiple periods, with the most concentrated being the macroscopic failure of the sample. When the coal sample approaches failure, large-scale cracks expand, so that low-frequency acoustic emission events increase most significantly. After the coal sample is destroyed, apart from fracture along the shear plane, the areas of local peeling and large-scale collapse are mainly caused by tensile failure