Abstract: In the room and pillar mining method,the size of the pillar will affect the strength of the pillar,the compressive stress to which the pillar is subjected,and the recovery rate of the mine.Under different mining depths,the compressive stress on the pillar is gradually increased,the allowable strength of the pillar is gradually increased,the size of the pillar is increased,and the recovery rate is reduced.In order to determine a reasonable pillar size,the strength of the pillar and the axial compressive stress were estimated using the Lunder and Pakalnis pillar strength theory and the dependent area method,respectively,so as to calculate the safety factor of the pillar,and on this basis,a reasonable pillar size was selected.By changing the mining depth,the size of the pillar at different mining depths can be calculated,and then the recovery rate can be calculated.

Key words: Roompillar method,Pillar strength,Pillar size,Safety factor,Recovery rate