Three-dimensional characterization of desiccation cracking behavior of compacted clayey soil using X-ray computed tomography

The shrinkage potential of clayey soils dominates their volumetric deformation and microscopic cracking behavior during desiccation processes and has profound practical consequences. To investigate the evolution of desiccation crack network in the compacted clayey soil, we apply a noninvasive approach integrating X-ray computed tomography (CT) and digital image processing technique. Representative geometrical parameters including soil mass area, shrinkage strain, crack ratio, average crack width, total crack length, and crack segment number are acquired from image analysis results to quantify the morphological evolution of desiccation crack patterns. Experimental observations show that cracks initiate at surface, propagate both laterally and downward into the soil body, and transit into massive networks due to coalescence and bifurcation. Quantitative analyses reveal the strong dependence of geometrical parameters on water loss through evaporation. The shrinkage and cracking potential of the clayey soil specimen attenuate with the decreasing water content, which significantly reduces the growing trend of geometrical parameters during the posterior stage of desiccation. The spatial variation of crack network evolutions under drying results from intrinsic soil microstructural heterogeneity and suction capillary-induced local stress intensity. The proposed integrated approach is of great significance to characterize three-dimensional soil desiccation crack patterns and brings new perspectives into the study of the hydro-mechanical behavior of clayey soils.