Experimental Study on the Influence of Cooling Rates on the Permeability Coefficient of Thawed Soil After Open Frozen

Adjusting freezing patterns is a critical technology in artificial ground freezing (AGF) projects to mitigate frost heave. The distribution of ice lenses formed under varying freezing patterns not only influences frost heave but also modifies the structure of thawed soil, thereby affecting the thaw settlement process. However, most existing research on freezing patterns has primarily focused on their impact on frost heave, with limited attention paid to thaw settlement. This study investigates the cooling rates at the cold side of open frozen systems, which are the key variables defining different freezing patterns, and examines their effect on the permeability coefficient of thawed soil. Experimental results demonstrate that the cooling rate significantly influences the soil permeability coefficient. This is specifically manifested as a 12.18-fold enhancement in permeability coefficients as cooling rates decrease from 0.5 °C/s to 0.005 °C/s. As the temperature gradient increases, the permeability coefficients increase. The minimum enhancement magnitude in the permeability coefficient was recorded at −75 °C. A decrease in the cooling rate leads to an increase in the permeability coefficient, particularly under high frozen temperature conditions. Utilizing the Kozeny–Carman permeability coefficient equation, a predictive model for the permeability coefficient of thawed soil was developed. In practical AGF projects, any freezing pattern can be represented as a combination of different cooling rates. By applying this predictive model, the permeability coefficient of thawed soil under any freezing pattern can be simulated using the corresponding combination of cooling rates. This study provides a valuable reference for predicting thaw settlement following artificial freezing construction.