Influences of temperature and moisture histories on the hydrostructural characteristics of a clay during desiccation

Abstract

This paper investigates the influence of temperature and moisture histories in terms of freeze-thaw (FT), wetting-drying (WD), and wetting-drying-freeze-thaw (WDFT) cycles on the hydrostructural characteristics of a clay that demonstrates aggregated and dispersed structures, during desiccation. Investigated hydrostructural characteristics include the soil structure, soil-shrinkage characteristic curve (SSCC, relationships between the void ratio, e and the moisture ratio, ϑ), and soil-water characteristic curve (SWCC, relationships between the ϑ and the suction, s). Experimental observations show that compaction-induced structural pores are rigid in the aggregated structure but not rigid in the dispersed structure during desiccation. They collapse during FT, WD, and WDFT cycles and are replaced by micro and visible cracks induced during WD and FT cycles. The amount and distribution of textural pores are similar in specimens with aggregated and dispersed structures. Textural pores shrink after FT, WD, and WDFT cycles. Structural changes due to temperature and moisture histories result in a significant reduction in the clay's water-retention capacity in the low suction range and the global shrinkage. However, they have little impact on the shrinkage limit and plastic limit. SWCCs in the high suction range, which are determined by textural pores, are semblable after cyclic treatments regardless of the different initial structures, indicating that FT, WD, and WDFT cycles result in similar textural pore systems. The slope of the SSCCs in the basic shrinkage stage reduces after FT cycles due to the development of FT-induced microcracks but is less affected by WD and WDFT cycles. The ϑ-s-e relationships of the clay with different temperature and moisture histories and initial structures are found to distribute on a unique surface, which is modeled using a modified SWCC equation and limited experimental measurements in this study.