A thermodynamically consistent extension of the constitutive equations of saturated soils to unsaturated conditions is often worked out through the use of a unique ’effective’ interstitial pressure, accounting equivalently for the pressures of the saturating fluids acting separately on the internal solid walls of the pore network. The natural candidate for this effective interstitial pressure i...

Constitutive equations of unsaturated soils are often derived in a thermodynamically consistent framework through the use a unique ’effective’ interstitial pressure. This later is naturally chosen as the space averaged interstitial pressure. However, experimental observations have revealed that two stress state variables were needed to describe the stressstrain-strength behaviour of unsaturated...

The mechanical behaviour of unsaturated soils is one of the challenging topics in the field of geotechnical engineering. The use of finite element technique is considered as a promising method to solve settlement and heave problems, as associated with unsaturated soil. Nevertheless, the success of the numerical analysis is strongly dependent on constitutive model being used. The well-known Barc...

In engineering applications involving mechanics of geomaterials, focus is generally put on the deformation of the solid skeleton so that a great interest is given to the definition of the stresses governing the skeleton deformation. The presence of one or several fluids within the porous space of these materials introduces a complexity in the choice of the stress state variables with respect to...

This paper presents an overview of elasto-plastic modelling of unsaturated soils. Alternative stress and strain variables that have been used in constitutive models for unsaturated soils are discussed. The use of an effective stress equation may simplify constitutive relations, but often result in a stress space that depends on the material state. In this case, the constitutive behaviour is emb...

Prediction method for undrained shear behaviour of unsaturated soils is discussed in this paper. Based on Original Cam Clay model, authors have proposed constitutive model for unsaturated soils that the effect of water content is incorporated into superloading surface concept. Firstly, stress path of constant volume shear test is formulated under constant void ratio condition. And relationship ...

In this paper a rate dependent model for unsaturated geomaterials is presented. The formulation and numerical predictions are compared with available experimental results and discussed. The constitutive laws for the description of the time-dependent mechanical behaviour of saturated and unsaturated geomaterials generalize the isotach approach to the elastoplastic strain hardening based constitu...