Investigation of Overburden Collapse Behavior and Optimization of Sectional Coal Pillar Widths in Deep-Buried Fully-Mechanized Top-Coal Caving Mining Faces

Abstract

Aiming at the problem that the irrational setting of the width of sectional coal pillar (CP) during the mining of deep-buried fully mechanized top-coal caving (FMTC) face is likely to trigger strong ground pressure disasters, this paper took the geological and mining conditions of Dongpo Deep-buried Coal Mine as a case for research. A combination of mechanical testing, physical simulation, numerical analysis, and theoretical evaluation was employed to investigate the overburden structure and ground pressure behavior in the FMTC face. This research explores the stress distribution and plastic deformation behavior of coal support structures with different widths in the context of secondary mining. It also examines the relationship between the CP’s width-to-height ratio, the load it carries, and its plastic failure behavior, ultimately establishing a stability criterion that considers the safety factor and risk of instability. The findings indicate an inverse relationship between the width-to-height ratio of CP and the load they bear, as well as the extent of plastic failure, while a positive correlation exists with the ratio of the elastic core area. When the CP width exceeds 18 m, the elastic core area ratio surpasses 69.4%, the safety factor exceeds 1.1, and the instability probability is below 45%. Based on these results, the study suggests that the sectional CP with a width of 25 m in Dongpo Coal Mine can be optimized, proposing that a width of at least 18 m between adjacent working faces is adequate for safe production. These findings have been successfully applied in the mine’s 406 FMTC face, yielding positive safety outcomes and notable economic benefits. The results offer valuable insights for optimizing CP sizes in similar deep-buried FMTC face under comparable geological and mining conditions, with substantial theoretical and practical significance.