Hydromechanical characterisation of a highly expansive clay

The hydromechanical properties of a South African expansive clay are reported. In this study,swell potential and swell pressure were assessed by two oedometric approaches, namely, the loading after wetting test and the wetting after loading test. The data indicate that predictions of swell pressure from the two approaches remain similar, whereas greater predictions of heave are obtained for the loading after wetting approach. It is also observed that the magnitude of predicted heave from the loading after wetting test is dependent on the soaking stress considered, with greater swell being obtained for lower soaking stresses. Measurements of primary drying and wetting curves illustrate appreciable hysteresis in the intermediate suction range (≈17 MPa). The discrepancy of this finding with that of a previous study is attributed to differences in fabric. Additionally, when examining the volumetric response of a sample subjected to a drying and wetting path, negligible hysteresis is observed when void ratio is plotted as a function of gravimetric water content. Conversely, when the shrinkage/swell curves are plotted in terms of suction, irreversibly volumetric changes are apparent.