Optimization of Collaborative Recovery Schemes for Remaining Pillars Under Backfill Constraints

Efficient and safe recovery of legacy mineral resources is of great significance for the sustainable development of mines. The gold−sulfur mine adopts the sublevel open stope subsequent filling, and a 6−meter bottom pillar was finally left between each middle section. In order to achieve the safe and efficient recovery of the bottom pillar of this mine, taking the remaining bottom pillar in the middle section from −620 m to −820 m of the mine as the research object, four stope structure parameters and three isolation column retention schemes are designed. Based on the relationship between the limit span of bottom pillar mining, the width of the isolation pillar and the height of bottom pillar mining, the optimization suggestions for the resource recovery of the bottom pillar are then put forward. On this basis, the stability of the coordinated mining of adjacent middle bottom pillars was studied, in order to improve the mining efficiency of the bottom pillars. The results show that when the mining height of the bottom pillar is 3 m, the limit span of pillar recovery is 9 m, and the corresponding width of the isolation pillar should not be less than 2 m. For a mining height of 4 m, the limit span remains 9 m, but the required isolation pillar width increases to 3 m. When the mining height reaches 5 m, the limit span decreases to 6 m, with the isolation pillar width similarly requiring a minimum of 3 m. These parameters ensure structural stability during sequential extraction while maintaining safe stress distribution thresholds. The optimized plan entails a sill pillar mining height of 5 m, an extraction span limit of 6 m, and an isolation barrier pillar width of 3 m. When the mining progress of the upper middle section is ahead of that of the lower middle section, the horizontal distance between its mining positions should be no less than 18 meters. The research conclusion is of guiding significance for similar mines.