Stability analysis of large-scale stope using stage subsequent filling mining method in Sijiaying iron mine

To improve mining production capacity, a stage subsequent filling mining (SSFM) method is employed for Sijiaying iron mine. The height of the stage stope is approximately 100 m. As there are farmlands and villages on the surface of the mine, the surface deformation should be controlled when the ore is mined out for the purpose of stope stability and minimizing surface subsidence. In this paper, according to the site-specific geological conditions, the self-stability of the stage-filling body was analyzed, and the failure mechanism of backfilling body was defined. Thus the relationship between the exposed height of filling body and the required strength was obtained. Next, the stability of backfilling body and the characteristics of surface subsidence due to mining of −450 m level were analyzed using physical modeling. Finally, a three-dimensional numerical model was established using FLAC3D, with which the surface subsidence and the stability of stope were achieved. The results show that the stope basically remains stable during the two-step recovery process. The maximum magnitude of the incline is 10.99 mm/m, a little larger than the permissible value of 10 mm/m, and the horizontal deformation is 5.9 mm/m, approaching the critical value of 6.0 mm/m, suggesting that the mine design is feasible for safety mining.