Regarding the stability of subsequent backfill bodies in mid-segment mine rooms, which lacks systematic research, the design of backfill strength mainly relies on experience and engineering analogies. In an effort to refine these practices, advanced techniques were employed at an iron mine to analyze mechanical parameters for various backfill compositions. This led to the development of a large-scale model for evaluating consecutive backfill operations across seven mine rooms. Numerical simulations helped to map out the plastic zones, stress distribution, and deformations after each mining phase, including the dynamics of potential slip surfaces within the backfills. It was found that backfill instability and failure predominantly occur in the lower sections, around the midsection, and near the ceiling. Consequently, a zonal backfill strategy is proposed, advocating for targeted reinforcement at identified weak points rather than uniform strength across all areas. This approach not only improves overall stability but also considerably reduces backfill costs.