Cascade rupture development mechanism of coal and gas outburst

Coal and gas outbursts constitute one of the most destructive dynamic disasters in underground coal mining operations, manifesting as sudden destabilization of coal seam potential energy and rapid fracturing within the coal-rock system. Although extensive research has investigated outburst mechanisms, the understanding of how localized instability evolves into systemic failure remains inadequate. An energy-driven cascading mechanism is introduced which couples coal fracturing, energy dissipation, sequential triggering, and energy amplification processes to characterize the dynamic evolution of outburst phenomena. Physical similarity experiments were conducted using a true triaxial outburst simulation system incorporating high-sensitivity infrasound detection technology to capture outburst evolution dynamics. The newly developed amplitude integral sequence analysis method revealed distinct biphasic evolution characteristics: An initial high-amplitude pulse phase (180～350 Pa, duration < 0.2 s) followed by a sustained low-amplitude phase ( < 100 Pa, duration 0.2～1.8 s). The step-wise growth pattern observed in the infrasound analysis sequence provided direct evidence of coal body cascade fracturing. A quantitative model for cascade fracture evolution was developed incorporating overlap triggering, proximity triggering, and cumulative area thresholds as key cascade criteria. Engineering case validation demonstrated the model’s capability in predicting outburst propagation paths and development scales, revealing three critical evolution stages: Initial accumulation (growth rate < 0.2 m/event), rapid cascade (growth rate 1.0～1.6 m/event, 5～8 times higher than initial phase), and decay termination (growth rate approaching 0). The fracture paths exhibited significant fractal characteristics under multi-scale observation, demonstrating self-similarity between local and global fracture patterns. Outburst development followed exponential growth laws, with the final scale determined by cascade phase duration, while energy storage conditions served as the dominant controlling factor throughout the process.