Numerical study of a desaturation process by air injection in sandy soil

This work aims to numerically study the desaturation process in a coarse-grained sandy deposit by means of air injection. It is well-known that the soil cyclic strength to liquefaction of a saturated, sandy deposit is positively affected by the presence of gas in the void space in either a dissolved or a free form. A numerical study is performed to investigate some of the factors affecting the desaturation advance and controlling the soil desaturation process by air injection. Among these factors are: a) soil-water characteristic curve and intrinsic permeability (hydraulic parameters), b) injection time, and c) standard approach to two injection wells placement. Only the standard mechanisms of biphasic flow are investigated (i.e., incompressible and isothermal biphasic flow in an isotropic homogeneous porous media with capillary effects).

Metastable states of silty clays during drying

An experimental research program has been carried out on the drying behaviour of normally consolidated silty clays with the aim of observing and interpreting state paths followed by soil samples under suction increase at zero external total stress. The behaviour of overconsolidated clays during drying is also discussed for comparison and shows the influence of stress history on the desaturation process. The drying state paths of normally consolidated reconstituted clay samples are plotted together with the corresponding isotropic normal compression lines, assuming equivalence between suction and effective stress for a fully saturated soil. The importance of the stress transmission mechanism in explaining the observed offset between the virgin drying line and the normal compression line is pointed out. Moreover, an energy-based interpretation of this volumetric offset is proposed in terms of fabric metastability.Key words: desaturation, drying, fabric, matric suction, silty clays, volume change.