Sydney soil model. I : theoretical formulation

In this paper a theoretical study of the behavior of structured soils, including both clays and sands, is presented. A new model, which is referred to as the "Sydney soil model," is formulated within the framework of critical state soil mechanics. In the proposed model, the mechanical behavior of soil is divided into two parts, that at a reference state and that attributed to the influence of soil structure. The reference state behavior is formulated according to the soil properties at the critical state of deformation, based on the concept of plastic volumetric hardening. The effects of structure are captured in the model by incorporation of the additional voids ratio that arises owing to the presence of soil structure. The formulation is generalized to include both isotropic compression and general shearing. In part I of this paper, a new theoretical framework for modeling structured soil behavior and the formulation of the proposed Sydney soil model are introduced. In part II of this paper, the Sydney soil model is employed to simulate the behavior of clays and sands, including calcareous clays and sands subjected to both drained and undrained shearing, and the performance of the model is evaluated.