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.