Abstract: Based on the unified hardening (UH) model of reconstituted soil, a UH constitutive model is developed for structured clay. In this model, the dynamically moving normal consolidation line (MNCL) instead of the static normal consolidation line(NCL) is used as the reference line in determining the reference stress; and a proper increment evolution equation is proposed for the MNCL to describe the soil structural decay. The proposed structured soil UH model can reasonably simulate many behaviors of the structured soil, including the isotropic compression, strain hardening, strain softening, shear-induced shrinkage, shear-induced expansion, undrained shear decompression softening and coupling effect between soil structure and soil density. Compared to the original UH model, the structured soil UH model includes 3 new model parameters, which reflect the soil structure degree, the structure decay rate and the plastic flow rule, respectively. Comparisons between the test results and the model predictions of the three natural soils indicate that the structured soil UH model can reasonably describe the main features of the behavior of the structured soil.

Key words: structured soil, moving normal consolidation line, constitutive model, structural decay, UH model