A state-dependent multi-mechanism model for sands

Abstract

A state-dependent multi-mechanism model for sands in three-dimensional space is proposed within the framework of critical-state soil mechanics. The mechanical deformation behaviour of sands is characterised with a macroscopic volumetric mechanism and a number of one-dimensional equivalent microscopic shear mechanisms (EMSMs) in various orientations. Each one-dimensional EMSM includes a shear deformation and a volumetric deformation due to dilatancy, which are described by a microscopic shear stress–strain relationship and a microscopic stress–dilatancy relationship respectively. The detailed relationships between the macroscopic and microscopic model parameters are established, and all microscopic model parameters can be defined explicitly or implicitly by soil parameters with a clear and easily understandable physical meaning. Moreover, a state parameter, ψ, defined by the difference between the current and critical void ratios at the same confining stress is used, relating the dilatancy and peak stress ratios to the critical stress ratio. Successful simulations of the responses of sands under drained, undrained, monotonic and cyclic loading conditions and during rotation of principal stress direction are obtained.