Observation of geogrid-aggregate kinematics via X-ray CT

Geogrids are widely used in pavement engineering to enhance the performance of unbound aggregate layers by providing confinement and improving load distribution. While their macroscopic benefits are well-documented, direct insights into particle–scale interactions remain limited. This study uses X-ray computed tomography (CT) to investigate the mechanisms governing the behaviour of geogrid-stabilised aggregates. Two cylindrical specimens – one with geogrid layers and one without – were subjected to uniaxial compression tests involving a loading and unloading stage, with X-ray CT scans taken at the very beginning and end. To evaluate the particle kinematics, the technique of digital volume correlation was used. The particle kinematics of the specimen without geogrids revealed peak displacements and rotations near the top of the specimen, gradually diminishing with depth and extending across its height. The geogrid-stabilised specimen, in contrast, exhibited more stratified displacement and rotation fields of lower magnitude. Particle-scale 3D kinematic analysis of this specimen confirmed that geogrids effectively reduced particle displacement and rotation magnitudes, highlighting their critical role in stabilising granular structures. These findings demonstrate the potential of X-ray CT coupled with full-field image correlation methods for advancing the micromechanical understanding of geosynthetic-stabilised pavements and guiding future design optimisations.