An elastoplastic model for gap-graded soils based on homogenization theory

Abstract

Naturally formed soils (e.g., residual soils and deposit clays) usually show an absent range of particle size. Frequently used by geotechnical communities worldwide, such gap-graded soils can be simplified as binary mixtures composed of fine soil matrix and coarse rock aggregates. In this study, an elastoplastic model is proposed for gap-graded soils based on a volume average scheme and homogenization theory. The proposed model incorporates a structural variable to account for the evolution of the inter-granular skeleton of rock aggregates. The model is then implemented in a numerical code by the linearized integration technique proposed by Bardet and Choucair (1991). It is shown that the model can predict a wide range of variations of the overall shear responses with the increase in volume fraction of rock aggregates. An isotropic loading induces a nonuniform stress distribution in gap-graded soils, where the stress in the soil matrix is lower than that of the rock aggregates. The stress path of the matrix is approximately parallel with that of the rock aggregates during triaxial shear loading. The proposed model contains only one additional structure parameter compared with the generalized modified Cam clay model, which can be easily calibrated from the data of a conventional triaxial compression tests. Comparison between our model predictions and the experimental data from literature indicates that the propose model can well reproduce the mechanical responses of gap-graded soils within a wide range fraction of rock aggregates.