An Experimental Study on Permeability Properties of Outburst Coal under the Coupling Effect of Multiple Factors

Through the experiments investigation on complete stress-strain of coal and the permeability of coal under different stress and gas pressures, the rules of permeability of coal samples under different conditions and the corresponding permeability evolution equation were established. The results show that the permeability of coal samples under certain gas and axial pressure will exponentially decrease when the confining pressure increase. The gas flow in coal has significant Klinkenberg effect. As the volume stress increase, the scope of Klinkenberg effect can also become larger. The relationship of confining pressure & permeability and gas pressure & permeability were obtained by fitting experimental data. Base on permeability test of complete stress-strain, we recognized that the curves between gas permeability and strain under different confining pressure have the similar change trends. Changes of permeability are closely related to the damage evolution of coal. According to the characteristics of permeability curves, considering the integrated effect of confining pressure, axial compression, and gas pressure, the permeability evolution equations of complete stress-strain was established with effective stress.