Research on variability of freezing-thawing cycle on basic physical and mechanics properties of clay minerals

The effect of freezing-thawing cycle is one of the main causes for destruction of frozen soil engineering. Under the effect of freezing-thawing cycles, tremendous changes will occur in the engineering properties of soil, which resulting in the deformation and failure of engineering in cold regions. By testing the physical properties and conducting spherical template indenter tests of kaolin (with the main clay minerals of kaolinite) and bentonite (with the main clay minerals of smectite). After repeated freezing and thawing tests, the changes in physical-mechanical properties of kaolin and bentonite under the effect of freezing-thawing cycle are examined, and the change rule of the physical-mechanics properties of the soil with different clay minerals under the effect of freezing-thawing cycle can be speculated. The results show that (1) the first 10 times of the freezing-thawing cycle have important effect on the physical and mechanical properties of kaolin and bentonite. After 10 times of freezing and thawing, with the increasing number of freezing and thawing time, the density of kaolin decreases and the pore ratio increases, and the density of bentonite increases and the pore ratio decrease; (2) changes in soil physical properties are not only related to the types of the soil samples, but also the essential effect of the mineral compositions of the soil; (3) kaolin’s long-term strength (C24) is much higher than that of the bentonite (C24). However, in the process of freezing and thawing, the change in the kaolin’s mechanic performance is larger, and the bentonite’s mechanic performance is relatively stable.