Microcracks-induced damage modelling for transversely isotropic rock
Résumé
In the present study a new micromechanical damage model is proposed for transversely isotropic rocks. The originality of this model lies in the fact that it accounts not only for the coupling between material structural anisotropy and damage-induced one, but also for the opening/closure status (the so-called unilateral effects) of evolving microcracks. Taking advantage of a recent study by Goidescu et al. (2013), a closed-form expression of the overall free energy of the microcracked medium is presented. This expression is implemented in an appropriate thermodynamics framework which allows formulating a complete constitutive damage model. The salient features of the model such as the coupling between anisotropies and its effect on the damage yield function and on the tangent operator of the model are illustrated and validated on the identification of a transversely isotropic argillite. It is shown that under direct tensile loadings (including off-axis tests), the theoretical mechanical responses predicted by the proposed model well capture experimental data. Owing to the above results, the response of the material is studied along a tension loading followed by an unloading and a reloading in compression in order to illustrate the so-called unilateral damage effects due to microcracks closure.
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