Stability Control Of Roadway Along Gob With Thick Coal Seam Sequential Mining In Xiaojiawa Mine

In order to solve the problem of large deformation of roadway along gob(double tunneling)under the circumstances of thick coal seam sequential mining,the deformation characteristics and reinforcing techniques of 211301 assistant carrying roadway under the influence of secondary mining in Xiaojiawa coal mine were studied,through the methods of mechanical experiments,field investigation,theoretical analysis,numerical simulation and field industrial test.Research shows that:(1)The surrounding rock deformation of 211301 assistant carrying roadway was divided into three stages: roadway excavation,mining of 211301 working face and mining of 211302 working face.When excavating the roadway,the range of plastic zone was 4m,and the vertical stress distribution chart in the 20m-wide coal pillar was a bimodal curve with a 12m-wide elastic core.During the mining of 211301 working face,the stress distribution chart from the lead working face 5m to the lag 5m was excessive from the double peak to the single peak.After the mining of 211301 working face,the coal pillar became a plastic coal pillar,and the vertical stress distribution chart in the coal pillar was a single peak curve.The maximum stress was 19.12 MPa,and the coal pillar still had carrying capacity.(2)The mining stress produced by the mining of 211301 working face had a significant impact on 211301 assistant carrying roadway.The severe impact range was from 10 m of the advanced working face to 60 m of the delayed working face.The deformation of the roof,floor,coal pillar and solid coal body were increased to 637.25 mm,487.58 mm,695.49 mm and 520.55 mm,respectively.The lateral supporting stress was the main cause of the large deformation of 211301 assistant carrying roadway.(3)When 211302 working face was mining,the leading impact range was 30 m.The maximum deformation of the roof,floor,coal pillar and solid coal body were 1171.33 mm,483.46 mm,623.53 mm and 424.62 mm,respectively(under the circumstances of original support).The high stress was transferred to the solid coal body,where the stress could reach 18.5 MPa.(4)On the basis of the original support,the reinforcing technology was proposed: the solid coal body was strengthened with steel bolts,which its size was ?20×2200mm and the array spacing was 800 × 800 mm,and a reinforced ladder beam was used to improve the integrity.The roof was reinforced with ?21.6×12000mm anchor cables and reinforced ladder beams.The array spacing of cables in AB segment was 1600×2400mm(the original array spacing was 1200×2400mm)and the array spacing in BC segment was 1200×1600mm(the original array spacing was 1600×1600mm).The bolt torque shall not be less than 300N·m,and the anchor cable pretension shall not be less than 250 kN.(5)The reinforcing measures were further tested in 211302 and 211303 assistant carrying roadways,and the timing of reinforcement was obtained.The effect of reinforcement before the pressure caused by the previous working face came(beyond 100 m to 200 m of the advanced working face)was better than that after the pressure.In 211304 assistant carrying roadway,the reinforcement support was adopted as initial support.After the influence of 211304 working face mining,the deformation of the roadway was small and met the requirements of production.The paper has 62 figures,6 tables,and 71 references.