Insight into the effect of biaxial compression strain on adsorption structure of bituminous coal matrix as well as gas diffusion and permeability properties by macromolecule simulation

•Rationality of macromolecular bituminous coal model was verified.•Effect of strain on adsorption concentration of CH4/CO2/N2 was analyzed.•Effects of strain on swelling parameters, mechanical parameters and cohesive energy density were elucidated.•Effects of strain on diffusion properties of gases were discussed.•Compression strain has dual effect of promoting and inhibiting coal matrix permeability.