ABSTRACT
The Barcelona Basic Model (BBM) cannot predict the mechanical behaviour of unsaturated expansive soils, and the Barcelona Expansive Model (BExM) for unsaturated expansive soils is complicated and the micro parameters and the coupling function from micro-structural strain to macro-structural strain are difficult to be determined. This paper presents an elastoplastic constitutive model from the macroscopic observation for predicting the hydraulic and mechanical behaviour of unsaturated expansive soils, based on an existing hydro-mechanical elastoplastic model for non-expansive unsaturated soils. The model predictions are performed on oedometer tests on compacted unsaturated sand-bentonite mixture. The tests include swelling tests under a constant net vertical stress and one-dimensional compression tests under different constant suctions. The comparisons between measured and predicted results indicate that the model can quantitatively predict the hydraulic and mechanical behaviour of unsaturated expansive soils.
