Porous or fractured unsaturated media : transports and behaviour

In order to study relationships between soil water properties and soil structural properties, a computer micro-model of soil is constructed. In this paper, we present first a general building method of a porous structure, including both pores and grains, with different levels of aggregation resulting from a fragmentation process. A fractal structure is obtained when self-similarity is imposed over the successive scales of fragmentation. Emphasis is put upon the modeling of the retention curve. A classical capillary model and methods coming from the percolation theory enable us to simulate qualitatively the primary and secondary loops of the well-known hysteresis of this curve. In the fractal case, theoretical analytical expressions proposed for adjusting retention data are tested. The unsaturated hydraulic conductivity is also calculated on the same simulated soil, by analogy with an electrical network. On the other hand, our structures are deformable and simulation proves to be a useful tool to investigate the behavior of swelling soils. (Résumé d'auteur