A study of the thermal physical properties of frozen soil in gravel layers

Artificial freezing method is widely used in metro construction which goes through some gravel sections. The physical properties of gravel layers are the key basis for the design of the freezing method, and researches on thermal physical properties of artificial frozen gravel layers are lacking. To examine the thermal physical properties of artificial frozen gravel layers, a study of the freezing temperature, thermal conductivity and volumetric heat capacity of gravel layers was carried out with instrument developed at home. The physical properties of gravel layers were compared with those of clay, silt, etc. The results indicate that the freezing temperature change of gravel is in line with the typical change role and the freezing temperature of gravel is -0.21 ℃, which is higher than that of clay and silt. The volumetric heat capacity of gravel is close to that of other soils. The ratio of volumetric heat capacity reduces with the increasing particle size in two situations (freezing and room temperature). The ratio of volumetric heat capacity of gravel is 1.19. The thermal conductivity of gravel is more than that of other soils titled in this paper. The thermal conductivity of gravel is 3.89 W/(m·k) in the freezing situation, which is 1.65 times the room temperature. The thermal conductivity of gravel is in line with the role that a bigger particle size causes a bigger thermal conductivity and can be calculated by the thermal conductivity of materials.