Study On Surrounding Rock Stability Control Of Narrow Coal Pillar Roadway Protection In Inclined Stope

Gob side entry retaining has been widely used because of its many advantages,but it is less used in steep coal seam.Different from gently inclined near horizontal coal seam,the occurrence conditions of steep coal seam are more complex due to the particularity of coal and rock sedimentary structure.Because the mine pressure behavior is different from that of gently inclined near horizontal coal seam,the roadway maintenance is more difficult.In order to solve the stability problem of gob side entry retaining in steeply inclined coal seam mining process,based on the occurrence characteristics of coal seam and the mining method of inclined seam,the field test of gob side entry retaining scheme was carried out by means of theoretical analysis,numerical simulation and field observation.The main research results are as follows:(1)Through numerical simulation,the distribution of ground pressure and the variation of displacement of roof and floor are revealed.When mining in the upper section,it is found that the most active area of roof and floor is the lower part of strike,followed by the upper part of strike,and finally the middle part of strike.When mining in the lower section,the most active area of the roof and floor in front of the working face is the lower part of the strike,the second is the middle part of the strike,and the smallest is the lower part of the strike.The change of roof and floor is mainly characterized by "floor micro uplift and roof subsidence",and the roof subsidence is far greater than the floor heave..(2)Through numerical simulation and field measurement analysis,the internal stress analysis and deformation failure research of the coal pillar are carried out.The deformation of the coal pillar is obvious in the range of 0-3m away from the roadway,and the range of 1-2m is the largest deformation area,which also provides the basis for the support design of the coal pillar.At the same time,the internal deformation and failure of coal pillar are divided into large deformation fracture area,small deformation fracture area,in-situ stability area and small deformation fracture area on goaf side.Among them,the in-situ stability zone is the key to the success of gob side entry retaining,which plays a role in controlling the fragmentation and degeneration of coal pillar.(3)Based on the original support mode and the law obtained by numerical simulation,the support scheme of gob side entry retaining with surrounding rock control technology is put forward.The support optimization scheme divides the field area into five parts: 1)original support section;2;2)Densify the basic support section;3)The supporting section is strengthened in advance;4)Lag strengthening support section;5)Basically stable.(4)According to the deformation degree of the roadway,it can be divided into six areas: 1)No influence area in front of the working face;2)Influence area in front of the working face;3)Strong area in front of the working face;4)Intense roof activity area behind the working face;5)Roof movement slowing down area behind working face;6)The basic stable area behind the working point.This is quite different from the gently inclined near horizontal coal seam,especially the area with strong mine pressure behavior in front of the working face and the area with intense roof activity behind the working face is obviously larger than that of the gently inclined near horizontal coal seam,which provides the basis for formulating surrounding rock control measures.