Dynamic change characteristics of adsorbed and free water in silty clay under freezing-thawing conditions

Abstract:

To investigate the dynamic characteristics of adsorbed water and free water in silty clay during freezing and thawing and explore the physical processes between soil and water during these processes, a novel layered nuclear magnetic measurement technique was employed. Freezing-thawing experiments were conducted under closed conditions on silty clay with water contents (mass fractions) of 21.1%, 16.8%, and 12.0%, respectively. The microstructure of the soil at different depths after freezing and thawing was scanned using an electron microscope. The experimental results indicate that as the soil freezing process continues, both adsorbed water and free water decrease at different soil depths, and the relative decrease in free water is greater than that of adsorbed water in both the frozen and unfrozen zones. During thawing, both adsorbed water and free water increase at different soil depths. Furthermore, freezing and thawing lead to a decrease in adsorbed water and an increase in free water in the frozen zone, while both adsorbed water and free water decrease in the unfrozen zone. After freezing and thawing, the number and volume of pores increase in the frozen zone, while they decrease in the unfrozen zone. The dynamic differences in adsorbed water and free water during freezing are related to the inhomogeneous spatial distribution of water molecule interaction potential. The redistribution of adsorbed water and free water in the soil before and after freezing-thawing is the result of the combined effects of water migration and changes in soil microstructure.