Mechanical Behaviors and Acoustic Emission Fractal Characteristics of Bump-Prone Coal under Different Loading Rates

Coal and rock dynamic disasters occur frequently in deep coal mining. The loading rate affects the mechanical properties and behaviors. Uniaxial compression acoustic emission (AE) tests of bump-prone coal under various loading rates were carried out, and the mechanical properties, AE spatiotemporal evolution, and spatial fractal characteristics were analyzed. The experimental results indicate that the uniaxial compressive strength is positively related to the loading rate, and the elastic modulus increases before decreasing with the loading rate. The failure strain is positively related to the loading rate, and the percentage of the compaction phase relative to the pre-peak phase decreases with the loading rate. The hit rate, absolute energy, AE events, and amplitude evolution of coal samples under various loading rates are the same, and the maximum of AE absolute energy and hit rate is positively related to the loading rate. The spatial evolution of AE events of coal samples under various loading rates is the same, showing a "slow increase -> slow increase -> fast increase -> rapid increase -> slow increase" trend. The spatial fractal dimension ranges from 2.1 to 2.9, and the evolution of coal samples under various loading rates is the same, exhibiting a downward trend.