DEM investigation into effects of polydispersity of multilevel morphology on shear behaviors of granular materials

Extensive efforts have been made to investigate the multilevel shape dependence of the shear behaviors of granular materials. However, the impact of shape polydispersity at each morphological level, inherent in realistic granular materials, remains understudied. This study aims to address this fundamental issue. The concept of the overall polydispersity index (OPI) is utilized to quantify polydispersity degrees in elongation index (EI), flatness index (FI), angularity index (AI), and roughness (RG), denoted as OPI EI , OPI FI , OPI AI , and OPI RG , respectively. Four series of granular assemblies with varying OPI EI , OPI FI , OPI AI , and OPI RG values are generated and employed in discrete element method simulations to prepare samples for triaxial shearing. The variation trends of both macroscopic and microscopic behaviors, as well as fabric anisotropy influenced by OPI EI , OPI FI , OPI AI , and OPI RG are analyzed in detail. These results are also compared with those from monodisperse samples to highlight the notable effects of particle shape polydispersity on shear behavior. Additionally, a prediction model for the shear behaviors of polydisperse samples is proposed by averaging the contributions of all constituent particle shapes within the sample. This model can serve as an effective bridge between shear behaviors of polydisperse and monodisperse samples.