Modelling Anisotropy of Unsaturated Soils Using Bishop's Stress
Résumé
The paper presents an elasto-plastic mechanical model for unsaturated soils which incorporates the effect of evolving fabric anisotropy on the stress-strain response. The model is expressed in terms of mean Bishop's stress p* (defined as p*=p+Srs where p is the mean net stress, Sr is the degree of saturation and s is suction), deviator stress q and modified suction s* (defined as s*=ns where n is the porosity). Comparison between simulations and experimental data from triaxial tests on unsaturated compacted kaolin samples indicate that the incorporation of anisotropy produces a significant improvement of predictions. In particular, the model predicts well both the volumetric and shear strains measured during suction-controlled triaxial tests on initially isotropic and anisotropic samples. Further developments are required to incorporate the constitutive relationship describing the water retention behaviour.