Study On The Stability Of Coal Pillars With Room And Pillar Remining In Residual Coal Seam

Recycling chain pillars is an important way to improve the level of mine mining and to increase the recovery rate of resources under Room and Pillar mining system.The easily applied room and pillar mining method was widely accepted by small coal mine in north of Shanxi province,which leads to the low recovery rate and leaves a lot of residual pillars.At the same time the residual pillars could provide material basis for spontaneous combustion of goaf,which might threaten the production safety.With resource integration proceeding,the issue of recycling corner coal and chain pillars has attracted general attentions of scholars and engineers recently.As affected by the superposition of the old pillar mining of coal seam,characteristics of mine pressure appearance,rock formations,feasibility determination and deformation of coal pillars during the recovery process might be greater different from traditional coal seam in room and pillar mining.This thesis,which based on the actual situation of room and pillar mining area of 5-2 coal seam in north of Shanxi,calculated the reasonable width of chain pillars;Through the numerical simulation,the stability of coal pillars in old mining area was analyzed and determination of stability of coal pillar group in composite residual area was established.According to the structure of the stope and the existing mining conditions,the rectangular pillar arrangement scheme in residual mining area was determined.The problems of the recovery of the remaining coal pillars with different widths in the residual mining area are studied,and the stress,displacement and plastic zone distribution of the coal pillars were obtained to determine the width of the coal pillars and optimize the recovery scheme.The results showed that any single pillar stability theory had limitations.According to the limit equilibrium theory and the established mathematical and mechanics model,the stable width of the chain pillar ranged 15.6-20.2 m.According to the empirical formula,the width of coal pillar was 28.6 m.The reasonable width of the pillar is 15.6-28.6 m in summary.Based on the overall stability of the existing goaf,the stability conditions of coal pillars were analyzed through numerical simulation,and the stress state in the most dangerous coalpillars was regarded as the criterion of the stability of coal pillars in the process of recovery.Taking the engineering factors into account,the layout of the pillar was adopted taking 6 and leaving 6.The stress,displacement and plastic zone of coal pillars were increased with the decrease of coal pillar width during the process of the recovery with four different widths.When the width of the pillar is less than 20 m,the stope had good stability;when the width of the coal pillar is 16 m,the stress concentration and the displacement of the coal pillars were increased,the plastic zone also was extended,which could not guarantee the stability of the coal pillars.This thesis provided a new idea for the recovery of the coal pillar resources and the evaluation of the stability in goaf.It provided a referential method for solving similar engineering problems and laid a good foundation for further enriching and deepening the research system of such problems.