DEM modeling of soil bottom-initiated radial desiccation cracking phenomenon

Bottom-initiated radial cracking is a special phenomenon for soil as it is subjected to desiccation. This study aims to simulate the initiation and propagation of radial cracks in soil using both experimental and discrete-element method (DEM) approaches. Under controlled conditions of constant temperature and humidity, a laboratory desiccation test of clayey soil samples with bottom-constrained boundary conditions was carried out to illustrate the soil bottom-initiated radial desiccation cracking behavior. The evaporation characteristics as well as the development of radial cracking initiating from the subsoil were captured. To simulate this phenomenon, a desiccation model based on discrete-element method was used in DEM. Based on the laboratory testing results, appropriate parameters are selected for the numerical simulations. The DEM approach was calibrated by reproducing the experimental results of radial desiccation cracking. Subsequently, the initiation and propagation mechanisms of this typical soil cracking phenomenon was analyzed and discussed. With the constraint of the bottom boundary, the initiation of radial desiccation cracking was associated with the arched distribution of inter-particle tensile force in the soil samples. The propagation direction of the cracks was perpendicular to the inter-particle tensile forces. Finally, the effects of basal friction, evaporation gradient and shrinkage parameter on the bottom-initiated radial cracks in the simulation were analyzed. The size of the bottom particles and interface bonding factor played a significant role in the effect of basal friction. Compared with the samples under uniform water loss conditions, the bottom shrinkage rate was relatively low for the sample under a gradient water loss. In addition, an increase in the shrinkage parameter of the soil particles led to a greater extent of crack propagation.