Modeling of Drying-Induced Soil Curling Phenomenon

Drying-induced soil curling is commonly observed in nature. In order to investigate the change of water distribution in soil caused by drying and curling, a series of drying tests is performed on thin soil layers in the laboratory. A discrete element model (DEM) is then proposed to simulate soil desiccation curling. The outermost particles are selected as the surface of the model to address the importance of surface evaporation. Moisture distribution change during drying is governed by both surface evaporation and moisture exchange between DEM particles. The results show that the model can capture the main features of the soil curling process from concave curling (? $\cup $) to convex curling (boolean AND $\cap $). The model enables variation in moisture gradient during the drying process. The trend of the curling development obtained from the model agreed well with the laboratory observation. A newly exposed surfaces in the model can provide a more realistic moisture distribution and influence the curling behavior. Generally, the drying-induced soil curling process and extent are associated with the change in moisture gradient along the depth. The movement of tensile stress concentration change from the upper layer in the early drying stage to the lower part of the sample in the late drying stage is the intrinsic mechanical factor responsible for the initial concave curling deformation and the subsequent fallback and convex curling phenomenon. Curling deformation in the present model is compared with other existing explanations on desiccation curling. The influences of evaporation rate and hydraulic conductivity on the model performance were also discussed. It is found that a higher evaporation rate and a lower hydraulic conductivity would result in a higher extent of curling during drying.

Automated summary

In this study, drying-induced soil curling phenomenon was investigated through experiments and modeling. The variation in moisture gradient was found to be a crucial factor contributing to the curling.