Abstract: In view of the problems in the determination of the size of small coal pillar along the hollow excavation roadway of thick layer expansive mudstone roof roadway in wangjialing coal mine,theoretical analysis and numerical simulation analysis are adopted in this paper.The theoretical calculation shows that the distance between the boundary coal body in the goaf and the fracture location of the basic roof in the goaf is 10.47 m.Numerical simulation results show that the maximum vertical stress concentration coefficient of coal body in goaf can reach 1.94,and the vertical stress value of coal body in goaf reaches 14.58 MPa within 5.5~10.5 m from the lateral coal wall.Considering the low strength of coal seam on the working face and the thick layer of expansive mudstone on the roof,5 m coal pillar was set for the working face.The results can not only optimize the bearing stress distribution of working face,reduce the difficulty of surrounding rock support along hollow excavation roadway,but also improve the coal mining amount and reduce resource waste.

Key words: Expansive mudstone, Digging along empty lanes, Numerical simulation, Coal pillar