Effect of freeze-thaw on hydraulic conductivity and microstructure of soft soil in Shanghai area

The artificial ground freezing method is a good reinforcement method and has been widely used in underground construction of China's southeast coastal areas, where the soft soil is widespread. However, it also brings several problems, such as frost heave, thawing settlement, differential settlement and structural leakage. The study material of this paper is remolded Shanghai forth layer soil, which is gray-black muddy clay soil. Several laboratory tests were carried out, such as freeze-thaw tests, hydraulic conductivity tests, MIP tests and SEM tests, to find out the effect of freeze-thaw on the hydraulic conductivity and microstructure of the study material. It is found that after freeze-thaw, the void ratio and specific pore area have decreased, while the average pore diameter has increased, which leads to the increase of hydraulic conductivity. The increase ratios of hydraulic conductivity and control pore diameter have the same variation trend. This study can provide some theoretical guidance for the application of artificial ground freezing method.