Study On Reasonable Width And Support Method Of Narrow Coal Pillar In Roadway Driving Along Goaf In Steeply Dipping Seam

Reasonable coal pillar width can maintain the stability of gob side entry,improve the recovery rate of resources,and realize the safe and efficient mining and sustainable development of the mine.In recent years,gob side entry driving technology with narrow coal pillar has been greatly developed in gently inclined coal seam.However,due to the influence of surrounding rock failure and stress distribution complexity in large angle coal seam mining,this technology is rarely used in steeply dipping seam.Therefore,the research on the distribution of lateral abutment pressure of coal pillar,the breaking law of overlying strata of narrow coal pillar,the reasonable width of narrow coal pillar and the support method of gob side roadway under the condition of large dip angle have important guiding significance to realize the safe and efficient mining of large angle coal seam.Based on the research background of air return roadway of 25222 working face in 2130 coal mine of Xinjiang Coking Coal Group Co.,Ltd.,the failure law and stress evolution characteristics of surrounding rock of gob side roadway in steeply dipping seam working face are systematically studied by means of field investigation,laboratory test,theoretical calculation and numerical simulationUnder the influence of mining in the upper section of working face,the peak value of lateral abutment pressure of coal body at the edge of goaf gradually transfers to the depth of coal body,and a certain range of plastic zone is formed inside the coal body.The distance between the basic top fracture position of overlying strata and the side coal wall of upper section is 2.47m.Under the conditions of different roadway sections and driving layers,the vertical stress concentration coefficient is relatively low when driving along the arc section of top coal.The roof subsidence is 279.25 mm,which is 96.27%less than that of driving along the rectangular section of top coal.The main failure mode of the upper right cornr of the roadway is shear failure.When the width of coal pillar is 6 m,a certain range of stable bearing area appears in the coal pillar,the displacement and plastic zone of surrounding rock of roadway are small,and the stability is improved,which is conducive to the anchoring of bolt.When supporting the special shaped roadway driving along goaf in large angle working face.The left-hand screw thread steel bolt with HRB335 bolt material is 2.2m in length,20mm in diameter,60kn in preload,600mm × 600mm in row spacing,7m in length and 1200mm ×1200mm in row spacing,which can effectively control the surrounding rock deformation of roadway,and the supporting effect is good.