Discrete-element method analysis of the state parameter

Using a series of true triaxial simulations, this study shows that the particulate discrete-element method (DEM) can capture the state-dependent drained and undrained response that is typical for sands. The most significant finding is that relationships between the initial state parameter and both the dilatancy at the peak strength and the difference between the peak and critical state strengths observed in the DEM simulations lie within the range defined by the experimental data. As indicated by the DEM data, this relationship is independent of loading path (intermediate principal stress ratio). The correlations between the initial state parameter and both the peak strength and the stress ratio at the undrained instability state are qualitatively in accordance with previously published laboratory data. The DEM data agree well with the NorSand constitutive model. The relationships between the state parameter and both structural anisotropy at the peak stress and the coordination number are explored. These findings extend current understanding of the capacity of DEM to capture the mechanical behaviour of granular materials and highlight the possibility of using DEM as a tool when developing advanced constitutive models.