ABSTRACT
Certain types of unsaturated bonded geomaterials, as for example residual soils, loess or volcanic deposits, are often characterized by the presence of two types of bonding effects, one due to cementation among grains and the other due to surface tensions in water menisci. In these soils unstable processes can arise from coupled hydro-mechanical degradation phenomena, which can even produce the vanishing of either of the two contributions. In this work, both mechanical bonding and partial saturation are accounted for within the same strain-hardening constitutive model. The constitutive model is then used in the light of a theoretical approach aimed at interpreting the onset of hydro-mechanical instabilities in unsaturated soils. Oedometric tests are numerically simulated, showing the possibility of unstable volumetric collapses taking place as a result of saturation processes. The influence of different degrees of initial mechanical bonding on the occurrence of such phenomena is finally investigated, pointing out the existence of a critical range of bonding percentages which exacerbate the potential for mechanical instability upon saturation.
