Quantification of Shape Properties and Their Effects on Particle Packing of Coarse-Grain Soil

Particle shape is known for its significant influence on the engineering properties of coarse grain soil. But it remains difficult to quantify how the different scales of shape properties will affect the macroscopic soil behavior individually. This study aims to select independent shape descriptors at different geometrical scales and evaluate the influence of particle shape irregularities on the particle packing of coarse-grain soil. With the aid of the digital image technique for 2D image acquisition of coarse grain soil particles, the shape properties were firstly quantified by the presented shape descriptors. Statistical analysis was performed to evaluate the independence of each shape descriptor and the most common independent descriptors; elongation, roundness, and texture signature were put forward. The proposed shape descriptors were then used to classify the collected particles and establish the particle shape library. The influence of each scale shape property on particle packing was systematically investigated using discrete element method (DEM) simulations of uncompacted void content test with predefined particles selected from the shape library. The simulated particles with specified shape properties were selected from the corresponding shape library. The numerical simulation results indicated that elongation and roundness significantly contribute to particle packing, while the influence of texture signature can be neglected due to its small variation in nature. The larger elongation and smaller roundness values were proved to increase the uncompacted porosity of coarse grain soil.