A volumetric model for structured soils based on soil structure instability and generalized suction theories

Abstract

A new compound model is developed to calculate volumetric strains of unsaturated and saturated structured soils. In this model, structured soils are regarded as the composite of undisturbed and disturbed parts, both of which are uniformly distributed. The proportion of the two parts can be calculated through the combination of a pore size distribution curve, a suggested geometric structural model, the structural instability criterion and constitutive models for remoulded soils. The overall volumetric strain increment includes three components: the elastic increment of the undisturbed part, the plastic increment of the disturbed part determined by the application of the generalized suction theory, and the structure collapse contribution which is particularly relevant to the change of void ratio from undisturbed soils to disturbed soils. The relationship between the angle-stiffness of the structural instability criterion and the degree of saturation is determined by the structural strengths revealed by compression tests of natural structured soils. The validity of this model was established by comparing calculated results with published experimental data of collapsible loess.