The Mechanism of Enhanced Spontaneous Combustion Risk of Coal Affected by Geo-Stress in Deep Mines

The geo-stress is increasing with the rising mining depth, which enhances the risk of coal spontaneous combustion (CSC). However, the enhancing mechanism of geo-stress on CSC has not been fully understood. To this end, the pore structure, free radicals, oxygen consumption rate (OCR) and apparent activation energies of unloaded coal under different stresses were studied through a BET experiment, an in-situ electron spin resonance (ESR) experiment and a gas chromatography experiment respectively. With an increasing stress, the pore volume and specific surface area of unloaded coal exhibited a tendency that first increased and then decreased, reaching a peak at 15 MPa. The g-factor and free radical concentration of the unloaded coal exhibited a similar pattern. During the non-isothermal oxidation process, the g-factor of the unloaded coal demonstrated a proclivity for decline and subsequent elevation with a rising temperature. The concentration of free radicals and the OCR of the unloaded coal exhibited a gradual increase with temperature. The unloaded coal exhibited the lowest apparent activation energy under a stress of 15 MPa, displaying a pronounced propensity for spontaneous combustion. This study provided a theoretical basis for the study on CSC in deep mines.