The permeability experiments had been conducted under the same pore pressure and side compression but different axial stresses, meanwhile the experiments with same pore pressure and axial stress but different side compressions had been studied. The experimental apparatus included the triaxial osmoscope of CGMS gas-liquid relative permeability test system and the constant temperature system. The coal samples used were collected from qidong coal mine of anhui province. The results showed that when the pore pressure unchanged and the compression was at a certain range, the permeability of coal decreased with the increasing of stress. While the compression was unloaded, the permeability could not return to the origin value. This was mainly because that the plastic damage was generated owing to the effect of stress and adsorption. And the coal permeability of triaxial was consistent with that of quasi-axial.
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