Characterization of crack extension in water-bearing coal based on acoustic emission multi-parameter evolution

This study explores crack evolution in water-bearing coal using uniaxial compression tests and acoustic emission (AE) multi-parameter analysis to address the threat of water in deep coal seams. It tests coal samples with different water saturations (0%, 60%, 80%, 100%). Results revealed that increasing water content significantly reduces peak strength and changes fracture behavior. Acoustic emission parameters exhibited four distinct stages: nonlinear compaction, elastic–plastic transition, crack assemblage evolution, and final failure. Moisture delays early stage cracking through lubrication and support but accelerates crack coalescence and energy release in later stages. AE amplitude is mainly distributed in the low range (0–70 dB), and peak frequencies cluster in the 5–23 and 25–50 kHz bands, providing potential failure precursors. These findings provide new insights into the hysteresis failure mechanism of saturated coal and support early warning and risk assessment in deep mining.