Upgrading SANISAND model to address continuous stress principal axis rotation: A conservative approach

The SANISAND models are known for their ability to simulate sands behavior with various properties under a wide range of loadings. Nevertheless, there is much room for improvement in simulating stress principal axis (PA) rotation effects. This study tried to address the continuous stress PA rotation problem following a conservative approach in preserving the SANISAND basic formulation. The inelastic response of the material under the stress rotation is regulated by a plastic intensity index as a function of the stress rotation rate with respect to the deviatoric fabric tensor and the non‐coaxiality between the stress and the plastic strain rate. The model performance is verified compared to the experimental data as well as other constitutive models. Supplementary discussions are provided to shed light on how fabric evolution results in a lower degree of anisotropy under continuous stress PA rotation. Based on continuum bounding surface plasticity, the proposed model addresses the fabric anisotropy effects on the severity of plasticity under continuous stress PA rotation.