Study on evolution law of permeability of small coal pillars under multiple mining damage conditions

Jin Jingjue; Zuo Cong; Meng Fanlu

doi:10.19896/j.cnki.mtkj.2025.03.008

Abstract：Studying the evolution of permeability characteristics of small coal pillars under the influence of multiple mining operations has important theoretical significance and practical application value for preventing and controlling disasters in adjacent goaf areas.Based on the dynamic pressure characteristics of small coal pillars mining in thick coal seams of the Carboniferous system in Datong mining area,numerical simulation methods are applied to determine the stress field distribution characteristics of small coal pillars under multiple min-ing conditions,providing a mechanical path for experimental research on permeability evolution characteristics.Using the DJG-II triaxial stress coal rock permeability dynamic testing device,the evolution characteristics of small coal pillar permeability at different mining stages were tested.The results show that the permeability of the coal sample under original rock stress condition is 0.06×10-3-0.26×10-3 μm2,the permeability of the coal sample was relatively increased by 138%-437%due to the influence of the first stage mining;the permeability of coal samples affected by the second stage mining decreased by 7.1%-7.8%compared to the first stage;the permeability of the coal sample affected by the third stage mining increased by 88%-182%compared with the second stage.After being damaged by three mining operations,the permeability of the small coal pillar increased by 6.88-27.45 times compared to its original state,and it no longer has the ability to isolate harmful gases and accumulated water in adjacent goaf areas.The research results can provide theoretical support for the flow field mutual disturbance and disaster prevention between the working face and the adjacent goaf under the condition of small coal pil-lar mining.