Study on support technology of gob-side entry retaining in isolated island coal pillar working face in the deep well

Taking the isolated island coal pillar working face in the deep well of Juji Coal Mine as the engineering background, the deformation mechanism of backfill-surrounding rock of gob-side entry retaining in the high-stress isolated island coal pillar working face in the deep well was explored. The mechanical structure model of surrounding rock of gob-side entry retaining was built, and the width and strength of backfill required by gob-side entry retaining were calculated. The rationality of width and strength of backfill was verified by FLAC^3D software simulation and field monitoring. The research results show that the roadside filling technology of high-water filling material is adopted for gob-side entry retaining in isolated island coal pillar working face, and the filling is carried out in the form of filling bags, so that the filling body can be effectively connected to the roof. The method of "anchor bolt and anchor cable combined support + roadside filling body" is used to support the coal pillar in the roadway. The reasonable width of backfill is 4.0 m, and the roadway deformation tends to be stable when the stress reaches 8.0 MPa. The on-site monitoring results show that the maximum roof subsidence of the middle coal pillar roadway does not exceed 50 mm and the side deformation of the backfill body does not exceed 40 mm within 30 days of mining in 23_down working face. Within 30 days after the end of coal winning, the roof subsidence does not exceed 20 mm, the maximum deformation of the backfill body is 348 mm, and the deformation of the coal gang is small, the maximum is 150 mm. The effect of gob-side entry retaining is good.