A microcracks-induced damage model for initially anisotropic rocks accounting for microcracks closure

We formulate a new micromechanical damage model for anisotropic rocks. This model accounts not only for the coupling between material initial anisotropy and the damage-induced one, but also for the opening/closure status (the so-called unilateral effects) of evolving microcracks. A closed-form expression of the overall free energy of the microcracked medium is implemented in an appropriate thermodynamics framework to derive a complete damage model for initially anisotropic rocks. The salient features of this model are fully illustrated. Then, its capabilities are demonstrated through an application to a Taiwan argillite subjected to direct tensile loading (including off-axis ones) for which the damage model well captures experimental data (mechanical response, growing damage rocks strength). Finally, the response of the studied rock along a tensile loading followed by an unloading and a reloading in compression is provided in order to illustrate the so-called unilateral damage effects due to microcracks closure. •An original micro–macro damage model is formulated for the mechanical behavior of initially anisotropic rocks.•The model explicitly couples the damage-induced anisotropy and the structural one.•It also accounts for microcracks closure effects.•Finally, we provide illustrations of the salient features of the model and its first validation by comparing its predictions to experimental data on an argillite.