Abstract: The optimization of coal pillar dimensions in a double-tunnel layout, influenced by multiple mining activities, alters its spatial permeability. This leads to more complex gas migration patterns between the working face with a small coal pillar and the adjacent goaf, as well as more intricate distribution of the spontaneous combustion "three zones". To address this, this study takes the 13212 and 13214 working faces of the Xiaojihan Coal Mine for a case study. We first determined the coal pillar size based on its bearing characteristics, and analyzed evolution of its permeability, thus revealing its gas migration patterns in the working face with a small coal pillar and adjacent goaf. Results show that: ① Under the double-tunnel layout, considering the impact of multiple mining activities on coal pillar bearing, the optimal coal pillar size was 10 m. ② Under the influence of secondary mining, the permeability of the 10 m coal pillar underwent changes within a zone extending 56 m ahead of the working face. ③ Compared with the original layout with a 30 m coal pillar, the 10 m coal pillar configuration reduced the maximum width of the oxidation zone by 8 m. A new annular oxidation zone formed in the adjacent gob (13214 gob), with a maximum impact width of 136 m.