Abstract: Structured soils with interparticle bonding have higher shearing ultimate stress ratio and less free dilatancy than the corresponding reconstituted soils. To overcome this defect, a moving critical state line (MCSL) in stress space is presented based on the structured unified hardening (UH) model mainly considering soil structure collapse. By developing new yield functions and modifying dilatancy equation, the structured UH model is extended to be applicable for bonding structured soil. In stress space, MCSL parallels to the traditional static critical state line (CSL) and moves toward the CSL as structure decays. The extended model adds 1 new parameter, namely the initial bonding stress, to describe initial bond between particles. Comparisons between test data and predictions of 4 structured soils indicate that the extended model is qualified in describing the behaviors of the bonding structured soils in isotropic compression, drained and undrained triaxial compression.

Key words: structured soil, bonding, moving critical state line, constitutive model, unified hardening (UH) model