Narrow coal pillar width reserve and surrounding rock control in Tongxin Coal Mine
In response to the serious loss of coal resources,as well as problems such as large deformation of surrounding rock and coal wall fragmentation caused by the reserve of wide coal pillars to protect the goaf during fully mechanized top coal ca-ving in extremely thick coal seams,taking the 5311 air return roadway of the 8311 working face in Tongxin Coal Mine as the engineering background,a study was conducted on the selection of the reasonable width of the coal pillar for protecting the roadway along the goaf by combining theoretical analysis,numerical simulation,and on-site observation.Research has shown that theoretical analysis indicates that when the width of the reserved coal pillar is about 6 meters,it can ensure that the 5311 air return roadway is located in the area where the support pressure of the coal body decreases and the stress yield area of the coal body along the goaf edge,which is conducive to the stability of the surrounding rock of the roadway.Based on 3DEC numerical simulation verification,the stability of the 5311 air return roadway with a 6 m coal pillar and the evolution characteristics of the stress distribution and plastic zone in the overlying roof,solid coal slope,and surrounding rock inside the coal pillar of the 8311 working face after mining along the goaf are studied.The on-site application results also prove the superiority and reliability of the narrow coal pillar excavation technology in fully mechanized top coal caving mining.