Boundary delineation and stability assessment of post-inrush water-immersed coal pillars based on integrated microseismic monitoring and field analysis

The stability of water-immersed coal pillars remains a significant challenge in coal pillar research, particularly during post-inundation recovery following water inrush incidents. Due to harsh underground conditions, direct sampling and analysis are often infeasible, hindering both engineering design and operational planning. Consequently, the analysis of coal pillar inundation based on field monitoring data has become one of the few viable approaches. This study utilizes microseismic data collected from panel 1314 at the Xiaoyun Coal Mine to delineate the boundaries of water-affected coal pillars, with the results verified through numerical simulations. Notably, the analysis reveals that coal pillars near the retreat end of the panel exhibit highly complex inundation characteristics, including irregular and abrupt boundary transitions. To better understand this behavior, in-situ stress measurements and bedding separation data were integrated to identify the dominant influencing factors and to elucidate the underlying mechanisms. The findings of this study offer important insights into the spatiotemporal behavior of inundated coal pillars post-inrush, and provide critical guidance for boundary delineation, panel design, and safe mine operations.