Evaporation and desiccation cracking of soils: Experiment evidence and insight on the freeze-thaw cycle dependence

The cracking of clayey soils in seasonally frozen regions is affected by cyclic drying-wetting and freezing-thawing. Understanding the mechanism governing soil cracking behavior is crucial for the construction and long-term operation of infrastructures and earthworks. In this study, a series of laboratory tests were conducted on clayey soils, including freezing-thawing tests and evaporation tests. The evaporation rate and surface cracks evolution were monitored. The cracking mechanism of soils were analyzed. Results show that both the initially unsaturated and oversaturated soils exhibit an increase in evaporation rate with increasing freeze-thaw (FT) cycles in the early stage. Under the same FT and drying conditions, initially unsaturated soils show a higher evaporation rate in the early stage than oversaturated soils, followed by a lower rate after entering the residual stage. In addition, cyclic FT accelerates the propagation of the number of crack segments, surface crack ratio, and total crack length, but weakens the propagation of average crack width. Moreover, it was found that for initially unsaturated soils, desiccation-induced matrix suction plays a leading role in producing wide, rough, and curved desiccation cracking patterns. While for initially oversaturated soils, freezing-induced ice pressure/cryogenic suction dominates, resulting in short, fine, and straight frost cracking patterns.