A 3D discrete model for soil desiccation cracking in consideration of moisture diffusion

Soil desiccation cracking is a common phenomenon on the earth surface. Numerical modeling is an effective approach to study the desiccation cracking mechanism of soil. However, no three-dimensional (3D) model in the literature can consider the influence of desiccation cracking on moisture migration. To fill this gap, this work develops a novel 3D moisture diffusion discrete model that is capable of dynamically assessing the effect of cracking on moisture diffusion and allowing moisture to be discontinuous on both sides of the cracks. Then, the parametric analysis of the moisture exchange coefficient in the 3D moisture diffusion discrete model is carried out for moisture diffusion in continuous media, and the selection criterion of the moisture exchange coefficient for the unbroken cohesive element is given. Subsequently, an example of moisture migration in a medium with one crack is provided to illustrate the crack hindering effect on moisture migration. Finally, combining the 3D moisture diffusion discrete model with the finite-discrete element method (FDEM), the moisture diffusion-fracture coupling model is built to study the desiccation cracking in a strip soil and the crack pattern of a rectangular soil. The evolution of crack area and volume with moisture content is quantitatively analyzed. The modeling number and average width of cracks in the strip soil show a good consistency with the experimental results, and the crack pattern of the rectangular soil matches well with the existing numerical results, validating the coupled moisture diffusion-fracture model. Additionally, the parametric study of soil desiccation cracking is performed. The developed model offers a powerful tool for exploring soil desiccation cracking.