Abstract:

The progress in constitutive models for unsaturated soils is briefly reviewed at first; and then the state of the art of elastoplastic constitutive models for unsaturated soils is summarized. This paper focuses on introducing an elastoplastic model coupling hydraulic and mechanical behaviour of unsaturated non-expansive soils. As an example, a coupled elastoplastic constitutive model proposed recently by the author et al. and its model predictions are shown herein for illustrating the structure of the coupled model and its performance. Hydraulic hysteresis in the soil-water characteristic is modeled as an elastoplastic process with the elastic region of the saturation degree. The effect of change in degree of saturation on the stress-strain-strength behaviour and the effect of change in void ratio on the soil-water characteristics are taken into consideration in the model; in addition to the effect of suction on the hydraulic and mechanical behaviour. By using the same values of the model parameters, hydraulic and mechanical behaviour of unsaturated soils can be consistently predicted under the control of suction or water content along various total stress paths. The elastoplastic constitutive model for unsaturated expansive soils and the application of the coupled model to the finite element computations are introduced in brief.

Key words: unsaturated soil, elastoplastic model, stress-strain relation, hydraulic behaviour, coupling