Quantitative analysis of the desiccation crack evolution in red clay based on digital image correlation technology

Red clay is prone to cracking in desiccating environments. The crisscross cracks compromise the soil structures and induce the instability of slopes. Under natural hygrothermal conditions, a desiccation test of red clay slurry was performed with a self-made device and digital image correlation (DIC) technology to study crack evolution, quantitatively analyse the relationships between moisture content, displacement, strain, and cracks. Results indicate that cracks usually initiate by subdividing and intersect at right angles with other cracks. Main cracks initiate earliest and have the longest duration, with stabilised main cracks being longer and wider than secondary cracks. DIC technology can dynamically monitor crack evolution. Based on strain concentration areas, the location of early-initiated crack initiation and the propagation trend could be preliminarily predicted. The failure strain in cracking was related to the moisture content, and crack evolution was related to the red clay Atterberg limits. The soil shrinkage exhibited anisotropic behaviour, with greater vertical shrinkage at the soil clod centre compared to the edges. In contrast, the horizontal displacement and maximum principal strain at the soil clod centre were smaller than those at the edges. Those findings contribute to providing guidance for formulating engineering geological hazard control measures.