Tracking particles in sands based on particle shape parameters

The acquisition of particle kinematics of deforming sands generally requires tracking the particles within the specimen. For this purpose, one particle tracking method based on particle polar radius functions (PR-Track) and a second method based on the SH spectrum of particle spherical harmonics (SH-Track) are presented. Both methods are applied to the acquisition of particle kinematics of a Leighton Buzzard sand sample undergoing shearing in a miniature loading apparatus using X-ray micro-tomography. The results are compared to those from a particle volume-based particle tracking method (PV-Track). It is found that PR-Track and SH-Track return particle tracking results with a high precision which is comparable to PV-Track. For the tested sample, PR-Track is about 0.4 times faster than SH-Track. Furthermore, PR-Track and SH-Track have a much lower computational efficiency than PV-Track. However, PR-Track and SH-Track do not require particles to be displaced in a similar manner to their neighbours, which is assumed by PV-Track. Particle tracking results from PR-Track and SH-Track are not sensitive to search region sizes. These features imply that PR-Track and SH-Track are capable of tracking particles of granular media undergoing a large and complicated deformation. This capability is verified in a simple case study by applying the methods to track particles undergoing particle column collapse.