Instability prediction model of remaining coal pillars under remining disturbance.

To address the instability timing problem of residual coal pillars under mining disturbance, their stress migration law and instability mechanism were studied via numerical simulation, physical simulation, and engineering tests considering residual coal remining in the 3101 working face of the Shenghua Coal Industry. The results show that as the mining progresses, the stress concentrates on both sides of the remaining coal pillar and empty roadway. When the first coal pillar in front of the working face loses its bearing capacity, the stress is transmitted forward, resulting in the advanced collapse of the empty roadway roof and an excessive load on the second coal pillar in front of the working face. Additionally, the critical value prediction model of the coal pillar stability safety factor fs ${f}_{{\rm{s}}}$ was constructed. If fs ${f}_{{\rm{s}}}$ is less than the critical value during the repeated mining period, the remaining coal pillar must be reinforced. A hollow grouting crossed anchor is selected for coal pillar reinforcement; thus, realizing the safe mining of the remaining coal pillars. Our research results provide theoretical support for the safe secondary mining of coal in China and similar coal mines worldwide. [ABSTRACT FROM AUTHOR]