Experimental study on evolution characteristics of coal permeability under triaxial stress conditions

GAO Han; CHENG Xiaoyu; ZHOU Aitao; ZHU Yuxuan; SHUANG Haiqing

doi:10.13347/j.cnki.mkaq.20250907

Abstract：Mining stress disturbance causes dynamic evolution of the pore and fracture structures of disturbed coal under complex loading conditions,leading to nonlinear changes in permeability,which significantly affects gas drainage efficiency.To address this issue,relying on triaxial test equipment,taking coal samples from the 150804 working face of Liuzhuang Coal Mine as the research object,and using an automatic coal core permeability measuring instrument,this study investigates the evolution characteristics and failure behaviors of coal permeability under different axial pressure,confining pressure,and gas pressure conditions,and analyzes the variation laws of permeability.The results show that within the range of axial pressure of 3 to 9 MPa,confining pressure of 1 to 3 MPa,and gas pressure of 0.2 to 1.0 MPa,the axial pressure and confining pressure are generally negatively correlated with the per-meability of the coal body.High gas pressure will cause the coal body fractures to close,resulting in a decrease in permeability.However,under high stress combinations,the variation range of permeability tends to decrease.The confining pressure compresses the pore structure of the coal body,and the permeability continuously decreases with the increase of confining pressure.When the axial pressure is 3 MPa and the confining pressure increases from 1 MPa to 3 MPa,the permeability decreases by 0.52×10-17 m2.The influence of axial pressure on permeability shows a trend of first increasing and then decreasing.In the initial stage(axial pressure of 3 to 5 MPa),due to coal body compaction,the permeability decreases.After exceeding the yield limit(axial pressure of 5 to 9 MPa),the internal fractures and cavities increase,and the permeability increases.