Experimental study of moisture content influences on permeability of coal containing gas

The relational expression between the moisture content and the permeability of coal containing gas was obtained through measuring the gas seepage flux under the combination of moisture, confining pressure and gas pressure by using a self-developed triaxial gas seepage testing system. Based on the experimental data of coal containing gas, some novel interaction results of seepage property influenced by moisture are obtained as follows: (1) For coal samples of different moisture content, the permeability of coal containing gas decreases with increasing of confining pressure under the fixed gas pressure condition; and the decreasing rule obeys an exponential law. (2) With the increasing in gas pressure, the permeability of coal samples decreases first and then increases, presenting a V style change trend and obvious Klinkenberg effect. (3) The influence of gas pressure on the permeability of coal containing gas is greater than the effect of confining pressure. (4) Moisture content has a significant effect on the permeability of coal containing gas under the constant temperature condition; and the permeability of coal containing gas slowly decreases with the increase in moisture content, following a negative exponential function law.