Micromechanics of unsaturated granular media

The homogenization method is used to study the properties of the strength criterion of a granular material in the dry, saturated, and unsaturated situations. Adopting a periodic description of the granular material at the microscopic level, the main features of the up-scaling technique are recalled. Then, a general definition of the strength criterion at the macroscopic scale is given in the framework of yield design homogenization theory. This approach makes it possible to find again classical properties of the strength criterion as a function of the properties of the granular material at the microscopic level. Furthermore, some experiments are presented in order to assess the accuracy of the model used to describe the unsaturated granular medium at the microscopic level.