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Desiccation crack is an important factor affecting engineering properties of clayey soils. In this study, the effects of compaction state and wetting-drying cycles on desiccation cracking behaviour of a clayey soil were investigated. Nine samples with various compaction water contents and dry densities were subjected to three wetting-drying cycles and the evolution of desiccation cracks was quantitatively described. The results reveal that both compaction water content and dry density play an important role in the development of desiccation cracks. Specifically, for the samples compacted on the dry side, desiccation cracks develop simultaneously. This phenomenon is also observed in samples compacted on the wet side with low densities. However, for the samples compacted on the wet side with high dry densities, desiccation cracks develop sequentially. Moreover, the higher the compaction water content, the faster development of desiccation cracks, and the smaller surface crack ratio, total crack length and average crack width. The higher the dry density, the slower development of desiccation cracks, and the smaller surface crack ratio and total crack length. Furthermore, the development of desiccation cracks can be divided into two stages according to the evolution of crack propagation velocity: (a) crack length extension, where total crack length increases rapidly with little changes in average crack width, and (b) crack width widening, where total crack length no longer changes and average crack width increases until it stabilizes. In addition, surface crack ratio, total crack length and average crack width all show an upward trend as wetting-drying cycles progresses. This tendency is more pronounced in the soil sample with a higher compaction water content and a larger dry density. • Effects of compaction state on soil cracking is investigated. • Three wetting-drying cycles are applied. • Larger compaction water content and dry density, smaller cracking degree. • Crack closure and rerouting during wetting-drying cycles are observed. [ABSTRACT FROM AUTHOR]

Tensile strength is a crucial mechanical property that governs the initiation and propagation of soil tensile cracks. With the global prevalence of warming effects and extreme climatic events, the recurrent freeze-thaw (F-T) cycles intensify the complex evolutions of soil pore structure and tensile strength in regions with widespread seasonal freezing or permafrost active layers. This study investigates the combined influence of F-T cycles and desiccation on the tensile strength of clayey soils. Specimens with varying compaction water contents (14.5%, 16.5%, and 18.5%) and dry densities (1.5 Mg/m3, 1.6 Mg/m3, and 1.7 Mg/m3) were prepared and subjected to cyclic F-T actions. A direct tensile test apparatus was utilized to measure tensile strength (σ t) along the desiccation path. Additionally, the changes in void ratio (e) and suction (s) during F-T cycles were analyzed to understand the mechanism behind the changes in σ t. Experimental results reveal that as the number of F-T cycles (N) increases, water content (w) declines at a decreasing rate and eventually stabilizes. With increasing N , the tensile displacement at failure and σ t show a pattern of initially decreasing and subsequently rising, with the inflection point typically around 1.5%–2.0% lower than the compaction water content (w 0). Under a few F-T cycles, soils compacted at the optimum water content and on the wet side exhibit higher void ratio and lower suction and σ t compared with dry-side compacted soils. However, this trend reverses with further increasing N. In addition, σ t increases as compaction dry density (ρ d0) rises within all water content ranges, primarily attributed to the significant interparticle cohesion controlled by a dense pore structure. The variation of σ t under F-T and associated desiccation is linked with the microstructural evolution characterized by aggregates, interaggregate pores and water-bridges. It is recommended to compact soils both on the dry side of the optimum water content and at the maximum dry density to enhance the freeze-thaw resistance of earth-works in seasonally frozen regions. • Freeze-thaw cycles with desiccation influence compacted soils' tensile strength. • Variations in void ratio and suction during freeze-thaw cycles govern tensile strength. • Soils with higher compaction water content exhibit greater expansion and shrinkage potential. • Dry-side compacted soils resist freeze-thaw risks better. [ABSTRACT FROM AUTHOR]