Generalized hydro-mechanically coupled hypoplastic constitutive model for unsaturated collapsible soils

In this paper, a generalized hypoplastic constitutive model for unsaturated soils based on the work of Fuentes and Triantafyllidis [2013] is presented. The constitutive model is formulated in terms of effective stresses, degree of saturation and suction. The main feature of the model is a Limiting Surface (LS) which describes the maximum achievable void ratio as a function of mean effective stress and degree of saturation. The LS allows to capture the wetting-induced collapse of initially unsaturated soils. The performance of the proposed model is demonstrated by backcalculation of a well-documented experimental study on over 30 samples of compacted Pearl clay by Sun et al. [2004] under isotropic as well as triaxial loading conditions. For this purpose, the proposed model is coupled with a hypoplastic model for the soil-water retention curve, which interrelates the effective degree of saturation with the suction and the void ratio.