Experimental Study on Pore Water Pressure and Microstructures of Silty Clay Under Freeze-Thaw Cycles

The variations on physical properties and microstructures of soils are essential to explore the freeze-thaw mechanisms. We do some experiments on freeze-thaw test of Qinghai-Tibet silty clay and cryo-scanning electron microscope (cryo-SEM) observing after freeze-thaw test and monitoring the changes of temperature, pore water pressure, and displacement. The results showed that the change of pore water pressure was closely related to soil particles rearrange, particle size redistributing, and then develop a new arranging tendency of soil pores during freeze-thaw cycles. During the period of soil freezing, the pore water pressure decreased gradually, and the particles became more gathering from point to point (P-P) form along with freezing rate decreasing, the relevant microstructures had changed from the matrix structure to gel structure, and pores became more simplex. During soil melting, the pore water pressure rose to stability, and the soil mainly experienced a consolidation process. In our study, we also quantify cryo-SEM images by Image-pro Plus (IPP) software. The results reflect the change of pore water pressure had a certain correlation with structural parameters under freeze-thaw cycles. These findings substantially contribute to understand the freeze-thaw mechanism and assist in upscale the microscale physical characteristic of frozen soil.