Process and Mechanism of Soil Desiccation Cracking Triggered by Surface Defects Based on DEM Modeling

Soil desiccation cracking is a ubiquitous natural phenomenon that intensifies under drought conditions. Experimental tests and field observations have shown that desiccation cracks often initiate at defects such as foreign inclusions, tiny pits, and uneven soil surfaces. However, the underlying mechanisms by which defects affect soil desiccation cracking remain poorly understood due to the lack of stress field information from laboratory tests. This study utilizes the three-dimensional Discrete Element Method to examine the micromechanics of how defects impact soil desiccation cracking. In this research, sand inclusions were used to model defects, and the effects of defect size, quantity, and distribution were carefully analyzed. The findings reveal that defects cause significant local stress concentration, triggering arc-shaped micro-cracks that eventually develop into Y-shaped cracking patterns. Defects influence the surrounding maximum principal tensile stress field within a range of 2–2.5 times the defect diameter. When a crack enters this influence zone, it is drawn toward the defect. The presence of defects increases soil heterogeneity, disrupting the sequential and hierarchical pattern of desiccation cracks observed in homogeneous soil specimens. Consequently, the crack network in soils containing defects consists of both orthogonal and non-orthogonal cracks.