A model for weakly unsaturated soils taking into account the three phases (air, water and soil)

While the effective stress approach appeared promising, it has been superseded between 1990 and 2000 by the independent stress theory, e.g. Alonso et al. (1990). This model enables the effect of unsaturation on soil and the collapse of unsaturated soil under wetting to be simulated which requires many geotechnical input parameters to be defined (empirical and real constitutive relations determined by a significant number of laboratory tests); Consequently, this model is primary a research tool and is not generally used for large geotechnical surveys or professional practice.