Determination method of rational position for working face entries in coordinated mining of section coal pillars and lower sub-layer

For the study of the layout of the roadway in the coal pillar and floor strata co-mining working face at the Zhaogu No.2 mine, a mechanical model of the segmental coal pillar within the working face was established through theoretical calculations. The analysis considered the stress state of the coal pillar area under different collapse conditions in the goaf after upper strata mining. Additionally, FLAC^3D numerical simulation software was used to simulate the stress distribution in the roadway for different layout positions during strata mining, thereby clarifying the impact of working face mining on the side roadway of the segmental coal pillar. The results show that the collapse of the goaf after upper strata mining significantly affects the stress distribution in the coal pillar area. To ensure safety during mining, roadway excavation and working face recovery should be conducted after the upper strata have fully collapsed during strata mining. The co-mining working face roadway should be positioned beneath the original upper strata goaf, avoiding stress concentration areas in the coal pillar location. Ultimately, it is determined that the side roadway for the lower strata working face should be arranged with an offset of 10 m outward. Practical on-site experience has demonstrated that under this offset, there is minimal deformation of the surrounding rock in the coal pillar side roadway, meeting the safety production requirements of the working face.