Abstract
Cyclic loading influences coal permeability and methane production. Experiments examining methane diffusion in a tectonic coal were performed at an adsorption equilibrium pressure of 0.6 MPa over a range of stresses from 0 MPa to 16 MPa. The results show that the methane diffusion in a coal matrix under cyclic loading can be modelled by a power-langmuir model, Qt = ati / (1 + bti). The parameters a, b and i are demonstrated to be related to the effective diffusion coefficient in the unipore model. The ultimate diffusion amount tended first to decrease, rise rapidly and finally decline again with increasing loading stress. The methane diffusion rates under several loading stresses exhibited three stages: rapid attenuation, slow attenuation and steady diffusion. Both the initial diffusion rate and the attenuation coefficient of the diffusion rate fluctuated slightly at first, increased steeply, and finally dropped as the stress increased. [Received: March 2, 2017; Accepted: October 24, 2017]
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