Research on the movement law of overburden strata during rotary mining of coal pillars in the main roadway under a chamber group

Rotary mining conducted on the main roadway coal pillar’s working face under a deep chamber group is influenced by various factors, including neighboring chamber groups and the pillar’s rotation. This situation presents challenges in maintaining roof stability and supporting the mining roadway. This study focuses on the 2317 working face of a mine in Shandong Province. By employing theoretical analysis, numerical simulation, and on-site monitoring, the impact of the chamber group on the stability of the overburden strata and surrounding rock of the lower roadway coal pillar working face is investigated. Additionally, the movement patterns of the overburden strata during the rotary mining of the roadway coal pillar under the chamber group are examined. The study reveals stress recombination in the vicinity of the chamber group, leading to the formation of a plastic through zone near the chamber. The stability of the roadway is primarily attributed to the stable rock layer and the minimal impact of distance from the working face on the overburden strata of the roadway coal pillar. As the working face advanced and the rotary angle increased, asymmetry emerges in the distribution of maximum displacement position of the overburden strata within the mining area, with a noticeable increasing trend in surrounding rock displacement. Upon the progression of rotary mining to the base of the coal bunker chamber group, a plastic connection formed between the bottom of the coal bunker and the roof of the working face, leading to yield failure, necessitating enhanced control of the roof. This study aims to elucidate the movement patterns of overburden strata and the deformation characteristics of surrounding rock during the rotational mining of coal pillars in underground chamber groups, offering theoretical underpinning for the safe and efficient extraction of coal pillars in such settings.