The aim of this study is to determine the optimal width of mine pillars that ensure stability under room-and-pillar mining conditions. A phosphorus mine in Guizhou serves as a case study for this investigation. The research integrates theoretical analysis, numerical simulation, and on-site monitoring to examine the load-bearing mechanisms of mine pillars and their appropriate widths within the context of room-and-pillar mining. Additionally, the study explores the impact of pillar width on quarry stability and validates the proposed optimization plan for pillar dimensions through simulation tests and practical engineering applications. The findings indicate that, following the initial excavation of the quarry, the maximum vertical displacement of the quarry’s roof plate varies at each stage. The displacement distribution is predominantly symmetrical along the quarry’s center line and decreases progressively towards the sides of the center line. As the excavation of the mining pillar advances through each phase of the quarrying process, a positive correlation is discerned between the displacement changes within the quarry and the exposed quarry area. Simultaneously, the displacement of the peripheral rock overlying the quarry demonstrates a gradual reduction along the left and right sides of the quarry’s center line. The displacement and settlement values of the surrounding overlying rock progressively decrease along these sides, culminating in a final displacement pattern that resembles an ‘arch’ shape. Following the excavation of each stage of the ore body, a high-stress region emerges within each stage of the mine pillar and the mining airspace. The quarry’s mine pillar enters a yield state, with the vertical stress on the quarry’s roof plate being significantly lower than that on the mine pillar. Tensile stress predominantly occurs around the mining airspace. The maximum vertical displacement and settlement value, as well as the maximum vertical stress value of the quarry, are recorded at 41.5 mm and 76.17 MPa, respectively. Notably, there is no significant plastic damage to the mine pillar, with damage being confined to localized areas. Empirical evidence from field engineering practice indicates that the theoretical analysis supporting an 8-meter pillar width is justified. Throughout the various phases of the ore body re-mining process, the displacement and settlement of the mine pillar remain minimal, with a recorded maximum displacement of 13.37 mm and a peak stress of 3.45 MPa, the reby confirming the pillar’s stability. These findings offer valuable theoretical insights and technical support for the safe and efficient extraction of phosphorus mines under analogous conditions.
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