Strength Properties Of Porous Media: Micromechanical Approach And Finite Element Analysis

S. Maghous


A micromechanical-based approach to the strength properties of porous media with a frictional solid matrix is presented. The analysis focus on the situation of non associated plasticity, commonly encountered for geomaterials.
A rigid-plastic behavior characterized by a Drucker-Prager yield criterion and a non associated ow rule is considered. The latter can be viewed formally as the limit of viscous behaviors with isotropic prestress. Extending the concept of limit stress states for such materials to the context of homogenization, it is shown that the macroscopic stress states can theoretically be obtained from the solution to a sequence
of viscoplastic problems stated on the representative elementary volume of the porous medium. The strategy of resolution implements a nonlinear homogenization technique performed in the framework of the modied secant method. This approach yields an analytical expression for the complete macroscopic strength criterion. It is found that the strength properties of the porous medium are not affected by the matrix dilatancy coefcient. A nite element procedure based on the equivalence between a problem
of limit analysis and a ctitious nonlinear elastic problem is also developed. The predictions of the micromechanical approach are then compared to the nite element solutions.

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