Abstract: The mine room goaf is limited by the unknown distribution of pillars in the mining area,the stability of mine pillars is difficult to control and other factors,a large number of mineral resources remain underground,which not only causes a waste of resources,but also may induce roof dynamic disasters. A mine in Shandong plans to carry out re-mining of the early left room pillar,and puts forward the method of pre-backfilling goaf and arranging fully mechanized mining face to recover mine resources. Therefore,a numerical model for checking the ultimate strength of mine pillar is established. The stability discrimination formula of mine pillar in the original state and the backfilling reinforcement is obtained. In both cases,the ultimate strength of mine pillar decreases nonlinearly with the increase of aspect ratio. The actual occurrence form of mine pillar in goaf is drawn based on CAD software,and the numerical model of pre-backfilling and re-mining of irregular pillar is constructed by introducing MIDAS NX software to study the stability of mine pillar and stope pressure of fully mechanized coal face with different advancing distances. The results show that when the working face is advanced to 120 m,the mine pillar near the working face is destroyed one after another,while in the case of backfilling,the stress in the elastic core area of all mine pillars decreases and the load does not reach the ultimate strength. The study results verify the feasibility of the method of recovering mine room pillars by cemented prefilling,which has certain reference significance for the recovery of idle resources. 

Key words: irregular ore pillar,regression fitting,stability,numerical simulation