Structural, volumetric and water retention behaviors of a compacted clay upon saline intrusion and freeze-thaw cycles

This study investigates the evolution of the structural, volumetric and water retention behaviors of a compacted clay during soaking and desiccation considering the influences of freeze-thaw (FT) cycles and saline intrusion. Compacted specimens were subjected to different FT cycles and then submerged in NaCl solution with different concentrations to facilitate the saline intrusion and measure the swelling behaviors. Shrinkage curve and filter paper tests were thereafter performed to reveal the clay's volumetric and water-retention characteristics during desiccation. Mercury intrusion porosimetry and field emission scanning electron microscopy tests were conducted to observe the evolution of the clay's microstructure. Experimental results show that the clay's micropores decrease and macropores increase after FT cycles, which is associated with the migration of water, growth of ice crystals, and development of FT-induced cracks during FT cycles. Similar observations were obtained from specimens after the saline intrusion, which is attributed to the osmotic and osmotically-induced consolidation. FT-induced cracks significantly reduce the clay's swelling and shrinkage potentials. FT cycles result in the shrinkage of micropores which leads to a reduction in the water retention capacity in the low suction range (capillary regime). The salinization suppresses the swelling of the clay and prolongs its primary and secondary swelling stages. The shrinkage potential initially increases and then decreases with increasing saline concentration. Salinization has significant influences on the osmotic suction and thus alters the clay's water-retention curves in terms of total suction. It demonstrates little impact on the clay's water-retention curves in terms of matric suction. (C) 2022 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V.

Automated summary

This study investigates the evolution of a compacted clay's structural, volumetric, and water retention behaviors during soaking and desiccation, considering the influences of freeze-thaw cycles and saline intrusion. The results show that both freeze-thaw cycles and saline intrusion significantly affect the clay's microstructure and water retention characteristics. FT-induced cracks reduce the clay's swelling and shrinkage potentials, while salinization suppresses the clay's swelling and alters its water retention properties.