Nucleation and propagation mechanisms of soil desiccation cracks

Contraction of soil during desiccation gives rise to polygon-patterned cracking. This phenomenon was investigated by continuous full-strain measurements on soil sample surfaces using digital image correlation techniques. The results show that desiccation cracking was of the mode I variety and can be reliably predicted through strain field analyses: the observed cracking was restricted mostly to high stretching domains. The observed high stretching stems from either external restraint or internal flaws of the shrinking soil. The cracks redistribute the stress in their vicinity and lead neighboring cracks to intersect them mostly orthogonally. As desiccation proceeds, the surface strain field ceases to provide useful information for predicting crack locations. Further analysis indicates that although drying occurs from exposed material surfaces, late-generation cracks actually initiate in the subsurface and express themselves subsequently at the surface. These observations offer insights into the intrinsic mechanisms of drying-induced crack growth in soils.