ABSTRACT
With thermodynamical laws and double variables theory, a theoretical framework for unsaturated soils has been established as an isothermal open system by Li without considering the temperature variation. However it has some limitations for it couldn’t fully embody the dilatant behavior for sands, Firstly, the model don’t take into account the anisotropy for granular materials, and dilatancy is the distinct characteristic differentiated from other materials which necessarily induces anisotropy during triaxial and shear tests, so dilatancy-induced anisotropy should be included to establish constitutive framework for unsaturated sands. In addition, the model in Li’s states the effect of solid phase on liquid phase depend on dSr . In fact, it is noted from Wheeler’s descriptions that the plastic deformation is attributed to the slippage at inter-particle contacts, and slippage at contacts will be inhibited by the presence of any meniscus water lenses which provide a stabilizing effect through an additional component of normal force at the contact. Experiments shows that the stabling effects are dependent on the number of meniscus water lenses at contacts, just as the plastic degree of saturation. From the above stated, this article defines granular materials (sands) as purely frictional materials and establishes solid-fluid elastoplastic constitutive framework considering the dilatancy and induced anisotropy resulting from the internal rearrangement during the shear deformation. In addition to seven assumptions included in Li’s, and the air pressure is assumed to be constant.
