Study On The Stability Of Narrow Coal Pillar Influenced By Main Roof Fracture Structure And It’s Application

Taking for No.8coal seam fully-mechanized coalface of YanJiahe mine as theresearch object, the technology of roadway driving along goaf of narrow coalpillar of fully-mechanized caving workface and the influence of stability ofnarrow coal pillar by main roof fracture structure, have been systematicallyanalyzed by laboratory experiments，theoretical analysis, numerical simulation andindustrial experiment etc, and optimization analysis of the narrow pillar width ofNo.8coal. Synthesizing the detection’s result of the main roof fracture structure,the creep characteristics of No.8coal seam and the optimization results of the coalpillar’s width, a reasonable width of the coal pillar was determined and theindustrial experiment was analyzed.Base on the space position’s relations of coal pillar, roadway and the mainroof fracture lines, the gob-side roadway’s overlying main roof fracture structuremechanical model was built, and3fracture structural forms of the gob-sideroadway’s overlying main roof’s was put forward, that the main roof’s fractureline located just at the outside of the pillar, at the top of the roadwayand,and at thewithin of the pillar. The stability of the entire roadway’s surrounding rock closelyrelated to the position of main roof’s fracture line locates. There were the largedifferences of the roadway’s surrounding rock stress and the pillar’s stress, as themain roof’s fracture line locates in different places. It was unfavorable to theroadway’s later maintenance as the main roof’s fracture line located just at the topof the roadway, otherwise it was favorable to the roadway’s maintenance as the main roof’s fracture line located just at the outside of the pillar. Therefore, whenthere was a roadway driving along goaf, we should considered that the main rooffracture structure have an impact on the stability of the narrow coal pillar, andavoid the main roof’s fracture line locating just at the top of the roadway. Whenthe width of coal pillar was3m, the roadway’s roof and the coal pillar were seriousdamaged, the bolt and anchor did not have a solid foundation, and it was difficultto maintain; when the width were5~7m, the roadway’s deformation werepermissible, although there was a certain degree damage of the coal pillar, butthey could still withstand the overburden load and meet the needs of a safeproduction, and the resource’s utilization rate were high; when the width were9~20m, the coal pillars in a accelerating creep deformation state, the roadway’sdeformation were severely damaged, the roadway’s later maintenance weredifficulty, and the resource’s utilization rate were low. The width of the narrowcoal pillar should not be too large, otherwise the stress of load would pass17.6MPa, then the coal pillar would be in the accelerated creep deformation state.When the main roof fracture lines located within the coal pillar3.42~3.87m, areasonable width was determined from5~7m.The research results were applied successfully at track transport roadway ofNO.8105and NO.8215, which showed the width of the coal pillar werereasonable,and the satisfactory technical and economic effects were obtained. Theresearch results could be applied in similar conditions.