François Nicot
Chargé de Recherche au Cemagref de Grenoble
Unité de Recherche ETNA - Risques Naturels & Vulnérabilité des Ouvrages
Domaine universitaire - BP 76
F38402 Saint Martin d'Hères Cedex
Multi-scale modelling of geomaterials using a micro-structural description

Many engineering issues involving geomaterials require to introduce a constitutive model which has to be well adapted to the type of loading. The importance of the micro-structure to deformational processes has been known for many years. Nevertheless, developing a constitutive model using micro-structural properties remains to be done.

This contribution focuses only on geomaterials which can be regarded as granular assemblies. Generally, on a small scale, the properties of the materials, whose size is equal to the size of the elementary particles described as rigid bodies, are quite simple. Complexity appears on larger scales (macroscopic scales), because purely geometrical non-linear effects occur inside a large number of particles. As a first approximation, we postulate that the mechanical behaviour of a material volume element depends only on the mechanical behaviour of intergranular bonds belonging to this volume. The mechanical behaviour of intergranular bonds can be expressed in a straightforward manner, involving very simple and generally well accepted constitutive models requiring only a few parameters. The constitutive behaviour of the material on a macroscopic scale can be derived from a microscopic scale description, taking a statistical description of the fabrics into account.

It seems that this type of approach could be applicable for a large range of geomaterials, such as snow material, or purely non-cohesive frictional materials (sand). First results of simulated usual tests are presented and commented.

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