Desiccation crack formation and prevention in thin bentonite layers

Desiccation cracks in clay play an important role in many geoenvironmental applications such as clay liners in engineered landfills, preferential flows and contaminant transport. In this study, a comprehensive series of experiments was conducted to investigate the desiccation cracks due to the combined effects of initial water content and layer thickness on bentonite clay. Slurries of bentonite were prepared with initial water contents ranging from 1200 to 2200%. The slurry was placed in a glass Petri dish and dried at a temperature of 30 ± 2°C. Results from the experiments were illustrated in a phase diagram, and it was found that the interplay between the initial water content and layer thickness has a significant effect on the formation and prevention of desiccation cracks. More specifically, a phase boundary distinguishing between cracked and non-cracked samples was obtained in the constructed phase diagram. A theoretical model based on the critical cracking thickness was developed and then was used to predict this observed phase boundary. Furthermore, a detailed morphology of crack patterns was investigated by employing image analysis techniques followed by statistical analyses. Findings from this study have potential use in clay liner design, where bentonite is used as the main material, as well as in other problems associated with drying soils.