Elastoplastic Model of Sand Based on Double-State Parameters under Complex Loading Conditions

Abstract

Based on the existing unified hardening model, the double-state parameters unified hardening (DPUH) model is proposed, which can take into account the initial density and confining pressure dependent characteristics and stress-induced anisotropy of geotechnical materials. The DPUH model uses 11 material parameters, whose physical significance is clear. It has the following characteristics: (1) the state parameter χ is introduced to reflect the effect of initial density on deformation and shear strength under monotonic loading; (2) the stress state parameter R is used to reflect the influence of stress history on the current elastoplastic modulus and strength; (3) in order to reflect the influence of stress-induced anisotropy on the stress–strain relationship, the rotational hardening rules are introduced to establish the mixed hardening parameters that meet the critical state condition and take into account the isotropic compression and rotation-hardening characteristics; (4) the double-state parameters model can be used to describe the cyclic mobility phenomenon under cyclic loading conditions. By comparing the test data with prediction results of sand, it can be adopted to simulate the stress–strain relationship for sand with a different initial density and confining pressure under complex loading conditions.