Correlation of fabric parameters and characteristic features of granular material behaviour in DEM in constitutive modelling

The anisotropic microstructure of granular materials has a profound effect on their macroscopic behaviour and can be characterised using a fabric tensor. To include of fabric in the critical state theory (CST), anisotropic critical state theory (ACST) was proposed by modifying the state parameter \((\psi )\) $(\psi )$ of CST to a fabric-dependent dilatancy state parameter \((\upzeta )\) $(\mathrm{\zeta })$ . Noteworthy that \(\uppsi\) $\mathrm{\psi }$ showed a very strong correlation with characteristic features (e.g. instability, phase transformation and characteristic state) of macroscopic behaviour and, as a result, it has been adopted in many constitutive models. While \(\upzeta\) $\mathrm{\zeta }$ aided the inclusion of fabric in ACST models, the correlation between \(\upzeta\) $\mathrm{\zeta }$ and characteristic features has not been evaluated in detail yet, although a large number of works are found on micromechanics and fabric only. In this study, a large number of discrete element method simulations for drained and undrained triaxial were conducted to evaluate the correlation between \(\upzeta\) $\mathrm{\zeta }$ and characteristic features. To this purpose, the correlation between stress ratio and both classic and dilatancy state parameter ( \(\psi\) $\psi$ and \(\upzeta\) $\mathrm{\zeta }$ ) were studied in important characteristic features (e.g. instability, phase transformation and characteristic state). It was found that this correlation was improved using \(\upzeta\) $\mathrm{\zeta }$ which might be due to the inclusion of fabric in our model. This observation is new and significant for inclusion of fabric evolution in constitutive modelling.