Reasonable Width of Segment Pillar of Fully-Mechanized Caving Face in Inclined Extra-Thick Coal Seam

Determining the reasonable coal pillar width of fully-mechanized caving mining in inclined and extra-thick coal seam is important to improve the coal recovery rate. In this study, a basic roof broken structure model of fully-mechanized caving mining was established and the distribution range of the internal stress field was calculated. Then, the evolution of stress and plastic zone of surrounding rock with different widths of coal pillar during the excavation and mining were analyzed by using FLAC3D. Finally, the deformation of surrounding rock of roadway was monitored by field test. The results show that the distribution range of internal stress field is 4.2–4.9 m and the coal pillar width is 8–35.4 m in combination with the geological conditions of the test site. During the retreat of mining face, the internal stress of the coal pillar changes from single peak to asymmetric double-peak, and the plastic zone develops gradually from the two sides of the coal pillar into the central section, producing a certain range of elastic nuclear zone. The reasonable pillar width is determined as 24 m by considering comprehensively. Field test shows that the roadway deformation is small and the surrounding rock deformation of roadway was effectively controlled. The research results provide beneficial reference for determining reasonable width of coal pillar and roadway layout with similar conditions. © 2020, Springer Nature Switzerland AG.