Research on mechanisms of roadway surrounding rock instability and stability control technologies during final mining period: a case study of the 51109 working face at Lijiahao coal mine

Abstract

To address the issue of surrounding rock instability in the retreat passage during the final mining phase of coal seams beneath goaf areas, ensuring rapid and safe equipment withdrawal, this study focuses on the 51109 working face (5-1 coal working face beneath the 3-1 coal goaf) at Lijiahao Coal Mine. Employing a combined approach of theoretical analysis, similarity simulation experiments, and numerical modeling, systematically investigated the stress evolution patterns in the retreat roadway’s surrounding rock during final mining, the optimal coal pillar width, and mine pressure control techniques. The results indicate that during the final mining phase, advance support pressure and coal pillar stress progressively accumulate, resulting in significant pressure transfer phenomena. The retreat roadway operates within a multi-pillar high-stress environment. Based on the Mark-Bieniaski coal pillar strength formula and numerical simulation optimization, the optimal width for the pillar protecting the roadway is determined to be 18m. Through coordinated regulation of pressure relief via mining cessation and forced roof caving, combined with optimizing the implementation location based on the fundamental roof limit cantilever length (11m), roof pressure can be prevented during face breakthrough. The research findings elucidate the mechanism of rock mass instability in the retreat roadway during the final mining phase beneath the goaf, providing scientific basis and technical support for roadway stability control under similar conditions.