Research on the coal pillar width and asymmetric control for gob-side coal entry in deep weak coal seams with strong dynamic pressure

LYU Feng

doi:10.11799/ce202501017

Abstract：Aiming at the large-scale instability and damage caused by coal pillars and surrounding rock support systems of the gob-side entry driving surrounding rock in deep weak coal seams with strong dynamic pressure,the deep horizontal coal roadway of Dongpang Mine is taken as the research object to reveal its failure mechanism.Theoretical analysis method was used to obtain the location of the fault line of the overlying main roof strata,and the numerical relationship between the size of the coal pillar and the internal and external stress fields,as well as the width of the limit equilibrium zone,was clarified.By introducing the deviatoric stress analysis index,the response characteristics of the deviatoric stress and plastic failure field of the surrounding rock of the roadway under different coal pillar widths were studied.The reasonable width of the narrow coal pillar was determined to be 7 meters.Based on the width of a 7 m coal pillar,the distribution of deviatoric stress and plastic zone in the surrounding rock of the roadway at different positions of the advance working face during mining was simulated and studied,and the strengthening range of individual pillars in the working face was determined.The degree of plasticization of the roof,solid coal,and coal pillar walls after stable excavation,as well as the boundary line position of the peak stress zone are obtained.It was clarified that the coal pillar side of the gob-side entry driving is the key area for surrounding rock control.The control measures for surrounding rock when designing support was elaborated,which require the anchor cable to pass through the boundary line of the peak stress zone of the surrounding rock and be within the relatively complete elastic zone in the deep part of the surrounding rock.A comprehensive treatment technology for surrounding rock was proposed,comprising"asymmetric channel steel truss anchor cable network on the side of the roadway+roof channel steel truss anchor cable joint point anchor cable+local fracture zone grouting modification+single hydraulic support advanced support".Engineering practice showed that the comprehensive treatment technology for the 7 m coal pillar and surrounding rock support technology determined by the research can ensure the safe recovery of the working face in deep weak coal seam with strong dynamic pressure.