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<p>The cyclic loading–unloading of pore pressure (CLUPP) significantly influences the destabilization and damage characteristics of deep coal–rock masses. However, the high compressibility of gas makes it difficult to replicate CLUPP on coal–rock masses in laboratory settings. In view of this, we conducted CLUPP seepage experiments on gassy coal under varying gas pressure conditions using the self-developed ‘THM-3 triaxial seepage test system.’ We further analyzed the effects of CLUPP on the mechanical behavior and seepage characteristics of coal. The results demonstrated that, during pore pressure loading, the coal’s axial compression deformation decreases while its radial expansion deformation increases; during unloading, the coal shows opposite deformation behavior. As the cycle period increases, the axial strain of coal shows a fluctuating increase, while the radial strain peaks during initial loading and then decreases in a fluctuating manner. This results in a continuous accumulation of total strain energy in coal. The continuous increase in total strain energy further reduces coal pore volume and decreases permeability. Notably, as pore pressure increases, coal’s axial and radial strains increase during each loading–unloading stage. Higher pore pressure causes greater permeability loss in coal due to CLUPP effects. When the pressure applied to the pores increased from 1 to 5&#xa0;MPa, the permeability loss ratio increased from 0 to 10.67%. Based on the experimental results, we developed a dynamic evolution model for the permeability of gassy coal under CLUPP, incorporating both internal and external stresses. The research findings offer significant theoretical insights into the instability mechanisms of coal–rock masses during deep mining processes.</p>

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Deformation and Seepage Characteristics of Gassy Coal Subjected to Cyclic Loading–Unloading of Pore Pressure

  • 期刊论文

  • 发表日期：

    2025年8月7日

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  • Shugang Li,
  • Chongzhi Wang,
  • Bin Zhou,
  • Haiqing Shuang,
  • Haifei Lin,
  • Shoujian Peng,
  • Biao Hu,
  • Han Yang,
  • Hang Liu

摘要

The cyclic loading–unloading of pore pressure (CLUPP) significantly influences the destabilization and damage characteristics of deep coal–rock masses. However, the high compressibility of gas makes it difficult to replicate CLUPP on coal–rock masses in laboratory settings. In view of this, we conducted CLUPP seepage experiments on gassy coal under varying gas pressure conditions using the self-developed ‘THM-3 triaxial seepage test system.’ We further analyzed the effects of CLUPP on the mechanical behavior and seepage characteristics of coal. The results demonstrated that, during pore pressure loading, the coal’s axial compression deformation decreases while its radial expansion deformation increases; during unloading, the coal shows opposite deformation behavior. As the cycle period increases, the axial strain of coal shows a fluctuating increase, while the radial strain peaks during initial loading and then decreases in a fluctuating manner. This results in a continuous accumulation of total strain energy in coal. The continuous increase in total strain energy further reduces coal pore volume and decreases permeability. Notably, as pore pressure increases, coal’s axial and radial strains increase during each loading–unloading stage. Higher pore pressure causes greater permeability loss in coal due to CLUPP effects. When the pressure applied to the pores increased from 1 to 5 MPa, the permeability loss ratio increased from 0 to 10.67%. Based on the experimental results, we developed a dynamic evolution model for the permeability of gassy coal under CLUPP, incorporating both internal and external stresses. The research findings offer significant theoretical insights into the instability mechanisms of coal–rock masses during deep mining processes.