Investigation of the failure characteristics of goaf roof in a metal mine using the acoustic emission technique

Accurately characterizing the deformation and failure behavior of goaf roofs in metal mines under stress is essential for mine safety and environmental protection. Uniaxial loading tests combined with synchronous acoustic emission (AE) monitoring were conducted on similarity models of metal mine goaf roofs. The mechanical response and AE spatiotemporal–energy characteristics during loading were systematically analyzed. Results show that the stress–strain curve exhibits four stages: initial compaction, elastic deformation, unstable fracture, and post-peak failure. The dominant failure mode is an “O–X” type fracture propagating along the roof’s long axis. The variation in AE temporal parameters effectively reflects internal damage evolution, with the transition from an AE quiet period to rapid activity and a sharp decrease in the AE R-value serving as reliable precursors of roof failure. The distribution of AE events intuitively reveals the evolution of damage locations and microstructural changes, and their statistical characteristics follow a normal distribution. Micro-damage mechanisms were further quantified using Average Frequency (AF) and Rising Angle (RA). A modified AE rate process model with strain as the independent variable was proposed, and a corresponding damage factor was established to quantitatively evaluate damage evolution at different loading stages. These results provide important theoretical support for goaf roof instability prediction and hazard prevention.