Multiscale failure modeling in granular soils

Abstract

Numerous materials can be regarded as granular – or quasi-granular – because a scale at which the granular micro-structure clearly appears can be defined. This scale is often denoted the microscopic scale. The micro-structure is composed of an assembly of elementary particles whose contact interactions can be described by simple laws. On the macroscopic scale, these materials behave as continuous media with an acceptable approximation; in a sample containing a sufficient number of particles, the granular structure may indeed no longer be visible, even if it continues to play a fundamental role on the macroscopic mechanical behavior. The local behavior on the contact scale can usually be simulated in a very straightforward manner by elastic-plastic laws to address the overall behavior of the assembly. In fact, the complexity of the constitutive behavior of granular assemblies does not stem only from the local properties, but also from the disordered packing. In the particular case of frictional granular materials that is considered throughout this paper, the influence of the packing is of paramount importance, since the local behavior can be roughly described by a simple elastic-plastic relation including Coulomb’s solid friction law. As a result, there is a clear advantage to developing constitutive models that embed a refined description of the micro-structure of the material.