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 \((\psi )\) of CST to a fabric-dependent dilatancy state parameter \((\upzeta )\). Noteworthy that \(\uppsi\) 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 \(\upzeta\) aided the inclusion of fabric in ACST models, the correlation between \(\upzeta\) 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 \(\upzeta\) and characteristic features. To this purpose, the correlation between stress ratio and both classic and dilatancy state parameter (\(\psi\) and \(\upzeta\)) were studied in important characteristic features (e.g. instability, phase transformation and characteristic state). It was found that this correlation was improved using \(\upzeta\) 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.