WANG Y F, LIU P, MA J H, et al.Deformation and permeability characteristics of raw coal under different gas pressures[J].Journal of Henan Polytechnic University(Natural Science) ,2026,45(2):148-155.

doi:10.16186/j.cnki.1673-9787.2025040033

Received:2025/04/16

Revised:2025/10/13

Published:2026/01/28

Deformation and permeability characteristics of raw coal under different gas pressures

Wang Yongfa1, Liu Po1, Ma Jianhong2, Gou Panfeng2, Wei Sijiang2,3

1.Hebi Zhongtai Mining Co.， Ltd.， Hebi  458000， Henan， China；2.School of Energy Science and Engineering， Henan Polytechnic University， Jiaozuo  454003， Henan， China；3.Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization， Jiaozuo  454003， Henan， China

Abstract: Objectives To investigate the deformation behavior and permeability evolution of raw coal under different gas pressures， and to clarify the mechanical-seepage coupling characteristics of coal under gas-bearing conditions.  Methods Triaxial compression-seepage experiments were conducted on raw coal samples under constant confining pressure and varying gas pressures. The permeability evolution during loading was analyzed. Based on the Mohr-Coulomb strength criterion， the cohesion and internal friction angle of coal under different gas pressures were calculated. A six-stage seepage evolution model was established to quantitatively characterize the relationship between permeability and volumetric strain rate.  Results Under constant confining pressure， coal permeability exhibits a distinct V-shaped variation with increasing axial stress. With increasing confining pressure， both the initial permeability and the peak-state permeability decrease exponentially. Increasing gas pressure weakens the mechanical parameters of coal， including cohesion and internal friction angle. According to the monitoring results of axial stress and gas flow during axial loading， the seepage process can be divided into six stages： stable adsorption， attenuation， gradual increase， abrupt increase， steady increase， and rapid surge. After the peak stress， gas permeability shows a linear relationship with the volumetric strain rate.  Conclusions This study reveals the dynamic evolution of coal permeability under the coupled effects of axial stress， confining pressure， and gas pressure， and clarifies the influence of gas pressure on coal mechanical properties and the permeability–deformation relationship. The results provide important theoretical support for determining pressure-relief zones， designing gas extraction sequences， and optimizing borehole parameters in protective seam mining.

Key words: gas pressure; raw coal; deformation characteristics; permeability characteristics