New experimental setup for 3D characterization of granular shape and associated morphological quantifiers

Mechanical response and behavior of granular materials are affected by particle shape parameters. However, the determination of a three-dimensional shape is complicated and requires advanced equipment and techniques which limits its feasibility. Accordingly, this study proposes a practical and economical setup for three-dimensional shape characterization. With the proposed setup, images captured by a regular camera can be used for three-dimensional quantification of granular shapes. The method involves using multiple images of grains and enhancement of several two-dimensional descriptors for three dimensions. The details of the proposed setup are outlined and descriptors that express three-dimensional shapes from two-dimensional images are presented. An open-source image processing program ImageJ is used to process the obtained digital images from the developed system for creating binary images and measurement of related parameters to be used in shape analysis and determination of particle shape descriptors. Seven different sand samples with various gradations and properties are investigated. Further, a series of laboratory tests aimed to focus on the effect of particle shape on the mechanical properties of granular materials including stress-strain and stress-dilatancy behavior. The results of laboratory tests revealed a meaningful relation between particle shape and mechanical properties. The developed imaging system is capable of two and three-dimensional shape characterization of granular materials. Accordingly, the proposed shape descriptors successfully indicate the shape parameters of a particle.