Comparison of model predictions of the anisotropic plasticity of Lower Cromer Till

This paper compares predictions, made using selected soil constitutive models, of the anisotropic plastic response of a sandy silty-clay, viz., Lower Cromer Till (LCT). The performance of four elastoplastic models, designated as MCC (Roscoe and Burland, 1968), S-CLAY1 (Wheeler et al., 2003), SANICLAY14 (Dafalias and Taiebat, 2014) and YANG2015 (Yang et al., 2015), are systematically evaluated based on a series of drained triaxial stress path tests, including virgin constant-stress-ratio (CSR) compression tests, probing stress path tests on initially K0 consolidated samples, and also various transitional CSR tests. Comparison of the various predictions shows that the isotropic MCC model cannot properly describe the mechanical behaviour of LCT due to its neglect of fabric anisotropy. The other three anisotropic models differ in their definition of the rotational hardening laws, particularly in the description of the equilibrium state of fabric anisotropy achieved under CSR loading. While significant improvements in model predictions can be observed from the three anisotropic models, for LCT S-CLAY1 generally tends to underestimate the volumetric deformation and both S-CLAY1 and SANICLAY14 are likely to overestimate the ratio of the deviatoric and volumetric strains for more anisotropic stress states. YANG2015 exhibits the most consistent performance in reproducing the mechanical behaviour of LCT among the four models under comparison. The importance of the virgin CSR tests to properly understanding the plastic anisotropy of soil fabric is highlighted.