4. Conclusion

Laboratory studies of the behavior of unsaturated soils have been made possible by the development, since the 1960s, of controlled-suction apparatus enabling the study of volumetric aspects of behavior, as well as shear strength properties. This work has been carried out using odometric and isotropic compression cells, shear boxes and triaxial cells. The most widely used suction control system is based on the "axis translation" technique, but some devices also use the osmotic technique.

Early approaches to unsaturated soil mechanics aimed to extend the use of a single stress, a function of total stress and suction, which would enable the effective stress approach to be extended to unsaturated soils. The phenomenon of collapse (also known as subsidence) of unsaturated soils during rewetting under load cannot be described using a single effective stress. The majority...