5. Unsaturated geomaterials

Until now, all the geomaterials we have considered have been either dry or saturated, the traditional assumptions in soil, rock and concrete mechanics. However, it must be recognized that in practice, in situ, geomaterials are generally in an unsaturated situation, i.e. the inter-granular voids are occupied by both a liquid (water, oil...) and a gas (air, water vapor, natural gas...).

The question of characterizing and modeling the mechanical properties of unsaturated soils is therefore a crucial one, but one that is still open internationally, particularly as regards the expression of effective stress (constitutive stress borne by the granular skeleton) in unsaturated conditions.