Coal damage by adsorbed gas has been observed and detected in a large number of experiments. Under the action of the adsorbed gas

the adsorption strain of coal is firstly generated

and then coal microstructure is rearranged

which will induce the coal damage and further deteriorate mechanical properties of coal. However

this adsorption-induced damage is usually ignored in the current coal-gas interaction models. Hence

it is necessary to propose a mechanical model for dual porosity medium

considering the adsorption-induced coal damage. In this study

a novel mechanical model was developed to accurately describe coal-gas interactions

including the routine mechanistic effect and the adsorption-induced internal swelling stress. Besides

the additional mechanical damage caused by these two coal mechanic actions was also studied. Research results show adsorption-induced coal damage

mostly in tensile mode

rearranges coal microstructure

and causes significant reductions of coal strength and Young’s module. It is found that the tension damage is the main reason for the gas adsorption-induced damage. In addition

gas with higher adsorption capacity will result in a larger rearrangement of coal microstructure and more significant damage

and it even may cause a new failure pattern. Furthermore

supercritical CO2 with a higher adsorption capacity results in greater damage and causes larger alterations of coal strength and Young’s module.