Biaxial shearing of star-shaped particles with multiellipse DEM model

¹ Department of Engineering Mechanics and Energy, University of Tsukuba, Tsukuba, Ibaraki, 305-8573, Japan
² Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL, 60208, USA
³ Civil Engineering Design Division, Kajima Corporation, Minato-ku, Tokyo, 107-8477, Japan

^* e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 1 December 2025

Abstract

Using the multiellipse-based discrete element method (DEM), we numerically study the biaxial shearing behavior of granular materials composed of star-shaped particles. These particle shapes are generated by overlapping two or three identical ellipses with a common center of mass, while varying the aspect ratio from 1 to 5. Our results reveal that the macroscopic shear strength of the system increases monotonically with particle non-convexity. In contrast, the packing fraction exhibits a non-monotonic dependence on non-convexity, initially increasing and then decreasing as non-convexity further grows. This behavior reflects variations in the local pore size due to the competition between short-range ordering and excluded volume effects. Furthermore, microscopic analysis indicates that the increase in shear strength is linked to higher contact numbers and reduced contact and inter-grain distances, corresponding to stronger interlocking at higher non-convexity.