Abstract
When undrained triaxial tests are performed, two main phenomena occur.
First, the compression of the sample produces an increase in the degree of saturation
and therefore, a reduction in the value of suction. Second, with the reduction in the
sizes of pores, the retention curves shift on the axis of suction. Thereafter, the
simulation of undrained triaxial tests requires the correct simulation of the
hydromechanical coupling phenomenon. A fully coupled constitutive model for
unsaturated soils is used herein to simulate the behavior of unsaturated soils subjected
to undrained conditions. The mechanical model is based on the modified Critical State
model and the effective stress concept. The hydraulic model uses the grain and pore
size distributions to approximately reproduce the structure of soils. This model is able
to simulate the soil-water retention curves during wetting-drying cycles. Plastic
volumetric strains modify the pore size distribution of the soil, which in turn affects
the retention curves and, therefore, the current effective stress. Some comparisons
between numerical and experimental results of undrained triaxial tests show the
adequacy of the model.