The homogenization techniques allow the macroscopic constitutive equat
ions of a given material to be derived from its microscopic behaviour.
The case of granular material is difficult because the microscopic le
vel must be described in discrete terms (contact forces and relative d
isplacements). The present paper is devoted to a general discussion of
this problem and to a presentation of different models for granular h
omogenization. Since we shall primarily be concerned with methodologic
al issues and with comparison to the standard microcontinuous case, at
tention will be focussed to the simplest case of micro-elasticity assu
ming a linear contact law.