Study on deformation control of gob-side entry retaining with roof cutting and engineering application

To reduce the coal pillar’s loss at thin and medium coal seam,a new technique,entry roof cutting,for gobside entry retaining without coal pillar has been put forward. That is to generate a structural plane of cutting seam by cumulative blasting between the roof of entry and the side roof of mined area in last working face,the structural plane may weaken the transfer of the mining face’s side roof movement to the surrounding rock and cut the roof along the cutting seam. The fallen waste rock separates the goaf and forms a gob,in addition,it fills the falling space to support the rock stratum above,finally,the gob-side entry retaining achieve its stability. The theory and numerical analysis of the mechanical model suggest that the cutting seam could change the rock beam structure,which could transfer the pressure of deformation of rock stratum,to the short cantilever rock beam structure which has low load and doesn’t transfer the pressure of deformation,thus could reduce the surrounding rock’s pressure and deformation of gob-side entry retaining. According to that principle,the technique has been put forward to combine reinforcing support in entry,supporting densely in the side of entry and the cutting seam of entry roof. The study shows a favorable effect in the project of roof cutting to form an entry within thin and medium coal seam in different conditions. The method could reduce the pressure from the move of rock stratum in mining and the deformation of surrounding rock effectively.