This paper deals with the plastic behaviour of partially saturated soils by modifying an existing model for fully saturated soils. The saturated soil model, formulated in the framework of generalized plasticity, considers volumetric as well as deviatoric strain hardening and takes account of the memory of past stress history and possible limit states. The generalization of the existing model to simulate the experimentally observed behaviour of partially saturated soils has been obtained by introducing Bishop's stress and suction as independent stress parameters and by modifying the hardening parameter and the yield condition to take into account the role of suction. Le comportement plastique des sols pardellement saturés a été étudié en modifant un modèle initialement développé pour les sole saturés. Le modèle des sols saturés, con¸u dans un cadre de plasdcité généralisée, étudle l'écrouissage des déformations volumétriques et déviatoriques et dent compte de la mémoire du matériau concernant l'historique des contraintes et des éats limites auquels il aurait pu avoir étésoumis. La généralisation de cc modèle aux sole pardellement saturés testés se fait par introduction de la contrainte de Bishop et de la succion, en tant que paramètres de contrainte indépendants, et par modification des parametres d'écrouissage et des conditions aux limites, permettant ainsi de prendre en compte le rôle de la succion.

Models for thermo-hydro-mechanical behavior of saturated/unsaturated porous media are reviewed. The necessary balance equations are derived using averaging theories. Constitutive equations are obtained using the Coleman-Noll procedure and thermodynamic equations for the model closure are introduced. A particular form of the governing equations is then solved numerically and the numerical properties are discussed. Application examples conclude the paper. There are 165 references in this review article.

Existing tumor growth models based on fluid analogy for the cells do not generally include the extracellular matrix (ECM), or if present, take it as rigid. The three-fluid model originally proposed by the authors and comprising tumor cells (TC), host cells (HC), interstitial fluid (IF) and an ECM, considered up to now only a rigid ECM in the applications. This limitation is here relaxed and the deformability of the ECM is investigated in detail. The ECM is modeled as a porous solid matrix with Green-elastic and elasto-visco-plastic material behavior within a large strain approach. Jauman and Truesdell objective stress measures are adopted together with the deformation rate tensor. Numerical results are first compared with those of a reference experiment of a multicellular tumor spheroid (MTS) growing in vitro, then three different tumor cases are studied: growth of an MTS in a decellularized ECM, growth of a spheroid in the presence of host cells and growth of a melanoma. The influence of the stiffness of the ECM is evidenced and comparison with the case of a rigid ECM is made. The processes in a deformable ECM are more rapid than in a rigid ECM and the obtained growth pattern differs. The reasons for this are due to the changes in porosity induced by the tumor growth. These changes are inhibited in a rigid ECM. This enhanced computational model emphasizes the importance of properly characterizing the biomechanical behavior of the malignant mass in all its components to correctly predict its temporal and spatial pattern evolution.

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