A damage model devoted to heterogeneous materials

11 February 2011

by S. Granet, EDF R&D / AMA and D. Seyedi, BRGM

The project « Nuclear wastes storage » at EDF R&D has engaged a partnership with BRGM for developing a damage model devoted to heterogeneous materials, in particular clay. This new model, called ENDO_HETEROGENE, has been implemented in Code_Aster by Nicolas Guy within his PHD works (BRGM and LMT-Cachan, see reference). The model can be used for instance for the simulation of rocks fracturation due to gaz injection.

This model takes into account the effect of rock heterogenity on its probability of cracking. A Poisson-Weibull approach represents the microcracks repartition at the initial state.

The model is integrated as a non-local damage model, based on the stress gradients. It contains two different thresholds : one of probabilistic crack initiation, one related to the stress intensity factor. These two thresholds are calculated with the regularized stresses. In fine, each finite element appears as either a healthy one, either a damaged one. For the moment, the model processes only the mode 1 crack (normal traction on the crack-plane).

Reference :

Nicolas Guy "Modélisation probabiliste de l’endommagement des roches : application au stockage géologique du CO2." Thèse de Doctorat, ENS Cachan, 2010

Damage of the clay because of tractions, on the surrounding area of a cavity subjected to high pressures
Sketch of a disposal cell for nuclear waste [Andra 2005]