ABSTRACT
The present work aims to investigate the influence of anisotropy on the prediction of unsaturated soil behaviour. The first part of the paper describes the improvement of an existing anisotropic elasto-plastic model for unsaturated soils. In the second part, the predictions of such novel model are compared with those of an isotropic elasto-plastic model and against experimental data for a number of triaxial and oedometric stress paths. In particular, elasto-plastic models for unsaturated soils can lead to incorrect predictions of the soil response during oedometric stress paths, especially if model parameter values have been selected on the basis of isotropic and triaxial tests. In this paper, particular attention has therefore been devoted to Ko conditions and to the investigation of the sensitivity of soil response to anisotropy during oedometric loading. Despite their experimental simplicity, oedometric tests are seldom used in the calibration of unsaturated constitutive models because of the uncertainties in the stress path resulting from the imposed radial constraints. Understanding the influence of anisotropy on the soil response during Ko loading is therefore an important step towards a wider use of oedometer tests during calibration of unsaturated elasto-plastic models.
