Research on bidirectional-reinforcement mechanism of narrow coal pillar of gob-side entry driving based on inflatable lock-type anchor

The bidirectional-reinforcement technology for narrow coal pillars in gob-side entry driving based on inflatable lock-type anchor is a new technology for retaining coal pillar support in gob-side roadway. In order to further study the reinforcement mechanism and optimize the support scheme of inflatable lock-type anchor, the coal pillar set in the gob-side entry driving of 04 working face under 123 coal seam in the Jining No.3 Coal Mine was taken as the engineering background, combined with the relevant conclusions of laboratory experiments and field industrial test, the FLAC3D numerical calculation software was applied to analyze the internal rupture characteristics and evolution process of coal body and load characteristics of inflatable lock-type anchor of the anchoring unit, the law of narrow coal pillar deformation and stress distribution and force of inflatable lock-type anchor of different reinforcement methods. The results show that the deformation of narrow coal pillar can be effectively controlled by inflatable lock-type anchor. The compressive stress area generated by the prestress of the anchor cable is symmetrically distributed. The conjugate shear failure zone is generated inside the anchor, and the angle between the conjugate shear band and the horizontal plane is about 45°. The distribution of axial load of cable has significant characteristics of stages. In the pre-peak stage, the axial force of the anchor cable is basically stable. In the post-peak stage, the axial force of the anchor cable increased significantly, and the load in the middle of the rod is larger than that at both ends. It is more reasonable for the anchor cables to adopt a double-row arrangement with a row spacing between 0.8×1.0 m and 1.5×1.0 m. The research results can provide strong support for perfecting the theory of two-way reinforcement of narrow coal pillars in gob-gob roadway excavation and further popularizing the technology.