气体吸附诱发煤强度劣化的力学模型与数值分析

在吸附性气体作用下，煤体将产生吸附应变，吸附应变通过使煤微观结构重新排列从而诱发煤损伤，并使其力学性质劣化。尽管大量试验证实了吸附性气体将会改变煤的力学特性，然而当前描述煤-气相互作用的力学模型并未将吸附诱发的损伤考虑其中，故也无法考虑气体吸附诱发煤强度劣化。基于此，建立一个考虑气体吸附损伤的双重孔隙介质力学模型，揭示气体吸附过程诱发的两个相互作用：一个是游离气体引起的常规弹性力学作用，一个是吸附气体诱发的内部膨胀应力，并在此基础上考虑两个力学作用所带来了煤的附加损伤。研究结果表明：气体吸附诱发煤基质产生细观损伤，以拉伸损伤为主，这使煤的力学性质劣化，表现为弹性模量和强度的降低。吸附能力越强的气体，诱发煤的微观结构改变越大，损伤越明显，甚至会诱发煤样呈现新的破坏形态。超临界CO2会诱发煤更大的损伤和强度劣化。

Mechanical model and numerical analysis of mechanical property alterations of coal induced by gas adsorption

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.