Effects of Coolant Temperature on the Characteristics of Soil Cooling Curve

The cooling curves of soil are graphs that represent the variation of soil temperature with time when it is cooled. Knowledge of soil cooling curves and their characteristic parameters play an important role in most thermal analysis concerning soil freezing and/or thawing. Understanding the effect of environmental temperature on these parameters may help scientists better understand how frost heaves happen and how to predict the occurrence of frost heaves more accurately. For soils with identical type, water content, bulk density, and initial temperature, we believe that the freezing process and associated cooling characteristic parameters would be independent of the variation of external environmental temperature. To test this hypothesis, we carried out a series of freezing process experiments on soils with identical physical properties under different coolant temperature conditions. Here, the coolant temperature represents the magnitude of the environmental temperature. Our results indicate that the coolant temperature affects soil cooling curve profiles by changing the critical parameters of nucleation temperature, super-cooling, and phase-transfer duration of water in soil pores. According to the magnitude of the coolant temperature, soil cooling curves can be categorized into three different types: a “regular” freezing process without or with a little super-cooling, a sudden and small rise in temperature after the super-cooling “dip”, and a permanent super-cooling of non-freezing process. We have shown that the freezing temperature of soils is not influenced by the variation of coolant temperature.