Principle and technology of surrounding rock control for gob-side entry retaining in deep mine gangue backfilling face

The intense mine pressure in the deep mine face makes it difficult to keep the gob-side entry stable. The use of gangue to fill the gob can effectively limit the large-scale breaking and movement of the overlying rock in deep stope,relieve the severe mine pressure in the deep mine face,and lay the foundation for the gob-side entry retention in the deep mine face. Through the field measurement and theoretical calculation,the movement characteristics of the overlying rock in the gangue-filled working face of the deep mine were discussed,and the bearing structure and stability of the surrounding rock of the gob-side entry retaining were discussed. According to the actual situation of the No.2305S-2 working face of Xinjulong Coal Mine,the roadside support structure was designed mainly by “gangue wall + concrete-filled steel tubular column”. It is proposed that “advanced support,strong surface protection,and deep anchoring” for the road retaining roof,“reasonable width,lateral restraint,and cooperative bearing” for the roadside support structure,“stress relief,impact resistance,and film control” for the solid coal rib,and the gob-side entry retaining surrounding rock control principle of “high stress deep transfer” of the road floor and the gob-side entry retaining surrounding rock control principle of “fixing the roof first → protecting the side → controlling the floor later”. The gob-side entry retaining surrounding rock control technology of “bolt + W steel belt” advance support and “long anchor cable + grouting anchor cable” permanent support was formed. The gob-side entry retention of No.2305S-2 deep well gangue filling working face in Xinjulong Coal Mine was successfully realized. The actual measurement of the surrounding rock of the gob-side roadway found that the deformation of the gangue wall of the roadway was uneven,the bearing capacity increased slowly,the concrete-filled steel tubular column was drilled to the bottom,and the roof anchor cable was easily broken. It is necessary to further strengthen the lateral restraint of the gangue wall and improve the bearing capacity of the gangue wall. A large plate is installed at the bottom of the CFST column to control the bottom drilling amount of the column and the roof anchor cable of the gob-side entry retention is required to have a certain elongation rate,so as to realize the coordinated deformation and bearing of the long anchor cable and the roof surrounding rock.