Characterisation of non-uniform deformation and desiccation crack formation in drying fine sediments using X-ray CT and particle tracking

Desiccation cracks in clayey soils reduce soil strength and increase hydraulic permeability, often posing challenges to the integrity of geotechnical structures. This study aims to investigate the three-dimensional (3D) non-uniform deformation and desiccation crack formation in fine-grained soils subjected to drying using X-ray computed tomography (CT). Samples with a flat surface or an initial surface flaw are dried in containers with different boundary constraints to investigate their impact on shrinkage and crack patterns. Micron-sized glass bubbles are embedded in bentonite paste as markers to track internal deformation with multiple scans during drying. A particle tracking algorithm based on Artificial Neural Network (ANN) is adopted to monitor internal non-uniform deformation before and after desiccation crack formation. Results reveal that soil shrinkage before the crack formation is non-uniform due to boundary constraints and the surface flaw, leading to various patterns of desiccation cracks. Soil shrinkage is restricted by sidewall constraint, causing a curved surface and crack formation near the sidewall. The surface flaw brings stress concentration at the flaw centre, resulting in pore size heterogeneity, faciliting air invasion and ultimately leading to crack formation. The research demonstrates the non-uniform shrinkage in drying fine sediments, which promotes uneven pore size distribution and desiccation crack formation.