Abstract: To study the relationship between the permeability of coal body and gas pressure, we established the mathematical models of coal permeability and gas pressure variation based on the analysis of ,stress and strain of coal body absorbing gas, and carried out the experiments in the condition that the temperature is constant, radial strain is restrained strictly and moisture remains invariable. Using the methods which measuring the gas seepage discharges of coal samples with different adsorptive characteristics under different pore pressures and pressure drops to determine the permeability. The seepage discharge was measured by water drainage method combined with the gas micro-flow meter method, and the measurement results were analyzed comparatively with the curve of mathematical model. The results show that the permeability changes with the gas pressure, and the influence degree of gas pressure is different for different adsorption of coal samples. The change trends of the theoretical gas permeability of coal samples and the experimental values are basically accordance, while the maximal relative error between the theory and experiment values reaches to 8.62%. Therefore, the permeability under a certain gas pressure can be calculated according to the basic parameters and mathematical permeability model of coal samples.

Key words: change of gas pressure, permeability, mathematical model, desorption-adsorption