Effects of clay content on the desiccation cracking behavior of low-plasticity soils

Effects of clay content on soil desiccation cracking characteristics were explored by testing three soils, i.e., a natural low-plasticity loess, the loess with clay removal, and the loess with 25% clay addition (denoted as soil-A, soil-B, and soil-C). The shrinkage and desiccation cracking of the three soils were interpreted with the assistance of mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM). Results show that clay content significantly influences soil shrinkage and desiccation cracking patterns. Different from soil-A, soil-B shows a structural shrinkage stage at the beginning of drying and soil-C has a non-zero shrinkage stage at the end of drying. These findings are because clay removal and addition produce many large-sized macro-pores (i.e., 21.34 μm) and small-sized micro-pores (i.e., 0.04 μm), respectively, as evidenced by SEM and MIP results. On the other hand, soil-A has single and “Y shape” cracks, while only the former crack is observed for soil-C. The lack of “Y shape” crack in soil-C is attributed to its homogenous skeleton and uniform pore size distribution because of clay addition. The desiccation cracking was absent in soil-B, mainly due to its small shrinkage capacity and homogeneous structure induced by clay removal. In addition, soil shrinkage and desiccation cracking occurred due to water evaporation in macro-pores.