Calcul numérique des tunnels boulonnés par une méthode d'homogénéisation

Adoptant le point de vue macroscopique, on décrit dans cet article une simulation numérique de la convergence d'un tunnel renforcé par boulonnage radial et/ou en front de taille. Les relations de comportement anisotrope du matériau homogénéisé, préalablement écrites, sont introduites dans un code numérique par éléments finis adapté pour la modélisation des phases d'excavation. En particulier, on y implante les formules de projection sur le domaine d'élasticité, nécessaires pour la résolution de l'algorithme itératif en plasticité.Une étude de cas est ensuite entreprise pour simuler les étapes d’excavation/renforcement d'un tunnel et calculer sa convergence au fur et à mesure que le front avance. En sus des deux modes de boulonnage, la prise en compte d'un soutènement en paroi est examinée, mettant en évidence l’interaction entre les différentes composantes de l'ouvrage : massif-boulons-soutènement. Des indications importantes sur les paramètres pertinents du renforcement ont pu être dégagées de cette étude, fournissant des éléments pour le choix d'un schéma de renforcement optimal.De par sa souplesse et son efficacité, cette méthode constitue un outil de calcul adapté au dimensionnement d'ouvrages géotechniques renforcés par des inclusions régulièrement réparties

Un schema de calcul multi-echellesde type elements Finis au carrepour la simulation de combustiblesnucleaires heterogenes.

National audienc

Elastoplastic behavior of jointed rock masses as homogenized media and finite element analysis

International audienceA comprehensive 3D formulation for the strength properties and elastoplastic constitutive equations of jointed rock masses are derived in this paper. The approach is based on the implementation of the homogenization method of randomly heterogeneous media within the frame works of limit analysis and elastoplasticity. A rigorous closed-form expression of the macroscopic strength criterion is first given as a function of the failure conditions of the rock matrix and of the joints. As an example of implementation of such a homogenized criterion, the stability analysis of an underground gallery in a jointed rockmasses is presented and the scale effects, which prevail if the number of joints is relatively low, are investigated through comparisons with the results derived from direct calculations. Assuming elastoplastic constitutive laws for the rock matrix and the joints, a micromechanical reasoning is used for the formulation of the overall behavior. The macroscopic elastic stiffness as well as the plastic criterion and the plastic flow rule are derived from the knowledge of the mechanical properties of the individual constituents. This anisotropic model is then implemented in a F.E computer code. Due to the multi-potential character of the macroscopic plastic flow rule, the numerical analysis is particularly focused on the iterative algorithm of plastic integration. Examples of numerical simulations dealing with jointed rock structures are finally given

Two-dimensional fi nite element analysis of gravitational and lateral- driven deformation in sedimentary basins

International audienceno abstrac

New developments in ALCYONE 2.0 fuel performance code

International audienceALCYONE is a multi-dimensional (1D, 2D or 3D) fuel performance code dedicated to pressurized waterreactors (PWR). This code is co-developed in the PLEIADES platform by the CEA, EDF and AREVA andsimulates fuel pellets and cladding evolutions during base irradiation, power ramps and accidental situations.Sophisticated chemical and physical models are used. The thermal and mechanical behavior is solved with the finiteelement method based code CAST3M.ALCYONE 2.0 is the next release of the code and includes several new features: improvements in incidental andaccidental situations modeling, new models available for 2D and 3D schemes and an evolution of neutron model tosimulate gadolinium fuel.ALCYONE 2.0 uses a new version of PLEIADES platform which allows the parallelized computation of rod axialslices in order to decrease computation times.To better simulate accidental situations, an axial transfer model for gases and a modeling of heaters for Loss OfCoolant Accident (LOCA) experiments have been added to the code. The axial transfer model can simulate an axialinternal pressure gradient in the fuel rod.For power ramps simulations in the 1D scheme, a new model for dish filling is available