Non-pillar mining of upper coal seam layers with double-roadway driving using a flexible-formwork pre-cast partition wall

Abstract

Abstract When mining layered coal seams, three-soft coal seams, high-gas coal seams, or hard-roof coal seams with the application of gob-side entry retention technology, various practical problems that seriously threaten construction safety arise, such as roadway deformation, shear failure of the roadway supporting body, and air leakage in the goaf. To effectively address these issues, in this work, a novel, pillar-free, coal mining technique based on a flexible-formwork pre-cast partition wall was proposed and applied to a case study: working face 2301 (upper) at Yuecheng Coal Mine, China. The principles of the technique and the characteristics of the movement in the surrounding rock were comprehensively examined. Through theoretical analysis and numerical simulation, the support parameters of the roadway and flexible-formwork pre-cast partition wall were determined and applied in the case study. From our analysis, it was demonstrated that the parameters of the flexible-formwork pre-cast partition wall and roadway support are reasonably designed, achieving effective roadway retention. Combined with a top cutting and pressure relief process, the roadway deformation can be eventually stabilised with the mining of the working face and does not affect the subsequent use of the roadway. From the acquired data, a good agreement between the field real-time measurements and the numerical simulation software measurements was found, which is helpful for the analysis of technological perspectives of the proposed framework. The introduced technology can effectively solve the technical problems existing in the traditional gob-side entry retention. It can not only realize non-pillar mining, but also double-roadway driving without coal pillars in 2301 working face can be achieved, which significantly improves the technical and economic index of the mine.