Compression model for cohesionless soils

A simple four-parameter elasto-plastic model describes the non-linear volumetric behaviour of freshly deposited cohesionless soils in hydrostatic and one-dimensional compression. It expresses the tangent bulk modulus as a separable function of the current void ratio and mean effective stress using natural strains. Specimens compressed from different initial formation densities approach a unique response at high stress levels—the limiting compression curve (LCC)—which is linear in a double logarithmic void ratio-effective stress space. The model describes irrecoverable, plastic strains which develop throughout first loading and represent mechanisms ranging from particle sliding and rolling at low stresses to crushing—the principal component of deformation for LCC states. The three input parameters describing plastic deformation can be readily estimated from a hydrostatic or one-dimensional compression test loaded to high stress levels; the elastic bulk modulus requires accurate small strain measurements in unloading. The model can be further simplified at low stress levels where compressive behaviour is controlled primarily by the formation density. Input parameters for a wide range of cohesionless soils are presented from which it is possible to infer the effects of particle mineralogy, size, grading and shape on compressibility. The model gives excellent predictions of measured compressive behaviour over a wide range of stresses and densities, and provides a useful basis for the construction of hardening rules for generalized constitutive models. KEYWORDS: compressibility; constitutive relations; plasticity; sands. Un modèle élastoplastique simple à quatre paramétres permet de décrire le comportement volumique non-linéaire de sols fraîchement déposés, sous des conditions de compression hydrostatique ou unidimensionelle. Il exprime, à partir des déformations naturelles, que le module matriciel tangent est fonction de l'indice des vides courant et de la contrainte effective moyenne. Les échantillons, comprimés avec différentes valeurs initiales de den-sité, tendent vers une même réponse aux fortes contraintes—la `limiting compression curve' (LCC) —réprésentée par une droite dans le diagramme biologarithmique indice des vides-contrainte effective'. Le modéle décrit les déformations plastiques irréversibles qui se développent tout au long de la premiére mise en charge, et les mécanismes présents, depuis le glissement et la rotation des particules, sous faible