A study of the influences of freezing temperature and thawing conditions on physical properties of marine soft soil before and after freezing-thawing

Difference in physical properties of marine soft clay before and after freezing-thawing is the key to study the thawing-settlement. This paper takes the typical soft clay in Ningbo as the research object, and the temperature (−5 ℃, −10 ℃ and −15 ℃) and the thawing conditions (forced thawing and natural thawing) are considered as the influencing factors. Indoor simulation experiment of freezing-thawing process was conducted to quantitatively analyze the differences in physical properties before and after freezing-thawing and to reveal the cause of the difference. The research results show that freezing and thawing results in the redistribution of physical parameters such as moisture content, dry density, pore ratio and permeability of the marine soft clay along the direction of freezing gradient. With the decrease in the cold junction temperature by 1 ℃, the change degree of water content, dry density and void ratio decreases by about 4% − 8%. When forced thawing is adopted, the change degree of soil moisture content is reduced by about 23%, and the change degree of dry density and void ratio is reduced by about 50%. However, the essential reason that different freezing-thawing conditions have various influences on physical parameters is the different amount of water migration and phase variables under different conditions. Thus, exploring water migration and revealing the effects on physical parameter is worthy of further study. The change in physical parameters of marine soft clay before and after freezing-thawing is closely related to the cold junction temperature and the thawing method, and the degree of change is easy to directly affect thawing-settlement. When designing the freezing method of marine soft clay and constructing, reasonable freezing-thawing methods should be selected to reduce the difference in physical properties.