The occurrence of dangerous coal and gas outbursts seriously threaten safety in underground coal mining. Thus, defining the spatio-temporal evolution of the mechanisms that contribute to these outbursts is of great significance in defining optimal countermeasures for outburst prevention. A dynamic system-based mechanism of coal and gas outbursts is proposed to define conditions that define the formation and instability criteria of outburst dynamics. A stress–damage–seepage coupled model is devised to represent gassy outbursts from the coal seam that couples elastic-damage and permeability evolution. Numerical solution of this coupling model is used to investigate the spatio-temporal evolution of coal and gas outbursts. The spatial scales of both the outburst system and the geological body are discussed, as well as countermeasures for prevention. We show that the outburst dynamic system comprises a gassy coal mass combined with a geo-dynamic environment and mining disturbance. The evolution through failure involves stages of initialization, formation, development then termination. The dynamic system forms when the mining damage zone and the tectonic damage zone coalesce. Stress transfer, gas migration, energy accumulation then release in the dynamic system are shown as key contributing features to the dynamic outburst, as well as the three-dimensional structure of the dynamic system and geological body. A released energy density greater than the required dissipation energy density is the key to determine whether an outburst can continue. This criterion defines countermeasures for outburst prevention that include unloading and depressurization, which either reduce the geo-stress or the gas pressure and content in the coal seam to avoid the instability criterion for the formation of the dynamic system.
All Science Journal Classification (ASJC) codes
- Civil and Structural Engineering
- Geotechnical Engineering and Engineering Geology