Abstract: Coupled process of coal deformation and gas flow has received considerable attention because of its importance in gas outbursts during coal mining. Coal permeability is closed related to its stress state. In this paper, coal permeability in the whole stress-strain process under various gas pressures, was measured for analyzing the effect of gas pressure on coal strength and permeability. Furthermore, some triaxial compression tests under the defined confining stress, not containing methane, were also carried out in order to neglect gas effects. Then according to porous media mechanics, coal porosities under different axial stresses were calculated based on coal stress and strain data of the triaxial compression tests. It is shown that the trends of coal porosity and permeability curves with the same effective confining stress are roughly same. Therefore, under triaxial compression, the effective confining stress has an important effect on the permeability evolution before coal peak strength. The more effective confining stress is given, the more coal permeability before coal peak strength decreases.

Key words: coal containing methane, permeability, effective confining stress, porosity