Abstract:To address the determination of a reasonable isolation pillar thickness under the special geological condition of a surface collapse zone, this study investigates a tungsten mine containing an active collapse area in Jiangxi Province. High-resolution topographic data were obtained through low-altitude UAV photogrammetry, and a three-dimensional numerical model integrating surface terrain, collapse geometry and orebody layout was constructed using Rhino and FLAC3D. Three isolation pillar thickness schemes—20 m, 25 m, and 30 m—were simulated to analyze the deformation characteristics, stress evolution, and plastic failure modes. The results show that the maximum surface settlement for the three schemes is 2.43 cm, 2.28 cm, and 2.03 cm, respectively, and the corresponding peak compressive stresses are 8.736 MPa, 8.724 MPa, and 8.713 MPa. Continuous and dense tensile plastic zones develop above the collapse area for the 20 m and 25 m pillars, forming a “strip + spot” tensile-weakening belt along the strike. In contrast, the 30 m pillar significantly reduces the extent and connectivity of the plastic zones, effectively suppressing tensile failure. Considering deformation control, stress attenuation, plastic zone development, ore loss and backfilling cost, a 25 m pillar thickness is recommended for general areas, whereas a 30 m thickness is preferable in the collapse-center sensitive zone to achieve a balance between safety and economy.