Evolution law and treatment of arc-shaped triangular zone at the working face end under thick bedrock

YANG Xijun; ZENG Fanwei; GONG Zhiqiang

doi:10.11799/ce202507011

Abstract：During the mining of thick bedrock working faces,large area of roof hanging is likely to occur at the working face ends,threatening the safe production of coal mines.To reveal the formation mechanism and evolution law of the arc triangular zones,we took the No.12407 working face in Huangyuchuan Coal Mine as the research background,and carried out theoretical analysis,laboratory tests,and numerical simulation.The results indicate that,affected by the high-strength roof rock,after the roof undergoes an"O-X"-shaped rupture,the hard roof at both ends of the working face are difficult to collapse,resulting in a large area of roof hanging and formation of an arc-shaped triangular zone.Theoretical calculations show that the distance of the hanging roof in the arc-shaped triangular zone at the end of the No.12407 working face is 20.1 m,which is consistent with on-site observations.As the working face advances,there are slight changes in the geometric shape of the arc-shaped triangular zone.Therefore,a hydraulic fracturing treatment plan was proposed,with hole arrangements at a raise angle of 40°,dip angle of 45°,hole depth of 30 m,and hole spacing of 20 m on the mining side,combined with hole arrangements at a raise angle of 40°,dip angle of 0°,hole depth of 30 m,and hole spacing of 20 m on the gob side,resulting in a reduction of 60%in the geometric structure of the hanging roof along the parallel direction of the working face and a reduction of 73.5%along the vertical direction.