Influence of inter-particle friction on the angle of repose and stress wave propagation in granular soils: a DEM study

In geotechnical engineering, the angle of repose (AoR) is widely adopted as an indicator of soil stability and particle interaction. However, AoR can arise from different combinations of inter-particle sliding and rolling friction, each representing different mechanical characteristics. This study systematically investigates the influence of sliding and rolling friction coefficients on AoR using the Discrete Element Method (DEM). Lifting cylinder tests were simulated while varying both sliding and rolling coefficients from 0.1 to 0.9 to examine their combined effects on AoR formation. Additionally, a stress wave propagation model was developed to simulate laboratory stress wave testing and to explore the relationship between inter-particle friction and wave response characteristics. The results reveal that while sliding and rolling frictions significantly influence stress wave responses, such as stress magnitude, particle velocity, and displacement, the AoR alone does not exhibit a consistent correlation with these dynamic properties. These findings suggest that AoR, although it is useful for static stability, may not be a reliable standalone indicator of dynamic soil behavior.