Comparison of the deformation characteristics of coal in gas adsorption-desorption process for raw and briquette coals

The deformation characteristics of coal during gas adsorption-desorption is investigated in this study, experiments are conducted on raw and briquette coals under different gas pressure. It is found that the strain curve of raw coal during the completely adsorption-desorption process can be divided into 6 stages, while there are only 3 stages for briquette; the swelling and shrinkage of coal with time during adsorption-desorption follow the Langmuir equation for both two kinds of coals; the adsorption induced swelling and desorption induced shrinkage were anisotropic for raw coal, while nearly isotropic for briquette; the relationship between the adsorption strain and equilibrium gas pressure can be described by the Langmuir equation for both two kinds of coals, and the relationship between the desorption strain and the initial gas pressure follows power function; residual strains after gas desorption are observed for both two kinds of coals; the swelling stage due to pressure relief in adsorption-desorption process can represent the characteristics of coal and gas outburst.