Abstract: To address the issue of foundation stability in construction engineering in cold regions, an experimental study was conducted to investigate the physical and mechanical properties of a frost susceptible silty clay in freezing process. Parameters such as the critical water content for frost heaving, frost heave forces, and shear strength of warm frozen soils were determined. The results indicate that frost shrinkage occurs when the water content of soil samples is below the critical water content for frost heaving. This phenomenon is attributed to the combined effect of frost shrinkage of the soil skeleton and phase transformation of pore water. The vertical displacement curves of soil samples exhibit three types with varying water content: frost shrinkage, frost shrinkage followed by rebound, and frost shrinkage followed by frost heave. The curve of frost heave forces can be divided into two stages, namely rapid growth and stable growth, due to the development of the temperature field. The frost heave force increases as the freezing temperature decreases. The increase in temperature gradient within the active zone of freezing soils, based on the theory of segregation potential, is the cause of higher frost heave forces. When compared to soil samples at normal temperature, the cohesion of frozen silty clay at -3℃ increased from 7.34 kPa to 29.56 kPa, and the internal friction angle increased from 6.40° to 9.18°. However, the shear stress curves did not exhibit brittle failure of frozen soils, but rather displayed characteristics of strain hardening.

Key words: silty clay, warm frozen soils, critical water content for frost heaving, frost heaving force, shear strength