Roof disaster analysis and prevention technology of mining in the thick conglomerate coal pillar area

Coal bursts from irregular coal pillar mining beneath thick conglomerate layers pose significant challenges in deep mining. This study analyzed overburden structure evolution and stress distribution at the coal pillar working face through theoretical modeling, numerical simulations, and field monitoring. It revealed coal burst mechanisms and roof failure prevention strategies. The results show that the mining process is influenced by the spatial structure of the surrounding stope, transitioning through stages of unilateral gob-side mining to bilateral gob-side mining, with the overburden structure evolving from C-type to S-type configuration. The coal body of the working face exhibits multi-level stress distribution characteristics. The coal pillars on the left and right sides are stress concentration areas, and the peak vertical stress increases with advancing distance. The main and sub-key strata II are the primary disaster-inducing layers during mining. The main controlling factors of coal burst are the dynamic loads from roof instability and high static stress in coal pillars. Accordingly, ground acid fracturing is proposed to weaken the disaster-causing strata, reducing the accumulation of roof elastic energy, improving the coal body stress environment, and enhancing buffering and energy absorption. After fracturing, the total fracture length is 380 and 275 m. Resonance exploration reveals extensive fractures in the rock strata with a 50% decrease in wave impedance. Microseismic events are characterized by high frequency and low energy with 103 J events decreasing by 63%. The results provide references for preventing coal bursts with similar roof conditions.