Angle of repose for superquadric particles: Investigating the effects of shape parameters

Abstract

This study develops a model for the angle of repose (AOR) of granular materials composed of non-spherical particles represented by a superquadric function featuring five distinct shape parameters. Our investigation integrates experimental and numerical analyses based on the lifting cylinder approach, using a total of 30 different particle shapes. Initially, we validate a superquadric-based discrete element method using spherical particles and two spheroidal particles, emulating m&ms and Pinto Beans. Subsequently, we examine the impact of each shape parameter on the AOR and heap geometry to identify the most influential parameters. We then construct the AOR model as a function of the particle aspect ratio defined using a combination of the shape parameters. To assess the accuracy and predictive capacity of the proposed AOR model, we conduct six blind tests involving particles with varying shapes and numbers. The results demonstrate a remarkable accuracy, with an average R2 value of 98.6%. Additionally, to showcase the practicality of the proposed AOR model, we apply it to estimate the internal friction angle and the soaked California Bearing Ratio (CBR) of dry sand samples. The results show estimation errors below one percent, underscoring the predictive accuracy and reliability of the model.