Permeability analysis of gassy raw coal under three stresses

By using the independently developed thermal fluid-solid coupled three-axis servo seepage device of gassy coal, the indoor seepage experiment under three stress factors of different axial pressure, confining pressure and gas pressure was carried out on the raw coal sample of Shanmushu Coal Mine. The results show that: when the constant gas pressure and confining pressure are constant, the coal sample permeability decreases nonlinearly with the increase of axial pressure, and the higher the confining pressure, the smaller the coal sample permeability; when the constant gas pressure and the axial pressure are constant, the permeability of the coal sample decreases nonlinearly with the increase of the confining pressure, and the larger the axial pressure, the smaller the permeability of the coal sample; when the constant axial pressure and confining pressure are constant, the coal sample permeability increases nonlinearly with increasing gas pressure. The sensitivity from the largest to the smallest of the three stress factors to the permeability of the coal sample is in the order of gas pressure, confining pressure and axial pressure.The single factor fitting results of three stress factors and the coal sample permeability show that the three stress factors are exponentially related to the coal sample permeability.