Experimental study on freezing characteristic curve of soils based on nuclear magnetic resonance technology

The freezing characteristic curve describes the variation of unfrozen water content with temperature in soils, and it is of engineering value to provide a model for calculating freezing characteristic curves suitable for different soil types. The freezing characteristic curves of six kinds of soils are tested by using the nuclear magnetic resonance technology, and a method for determining parameters of Michalowski model describing the freezing characteristic curves of soils is given. The influences of the initial water content and soil properties on the freezing characteristic curve are analyzed, and the model is improved by using the characteristics of Michalowski model parameters. The study shows that the freezing characteristic curve is independent of the initial water content, and that of the soils with different initial water contents is the same during the freezing process. Without considering the influences of temperature, the model parameter w_a is approximately equal to the maximum of bound water content in the soils, which can be used as an important index parameter to analyze and evaluate the characteristics of clay. The practical value is improved by the single-parameter Michalowski model as it performs well in predicting unfrozen water content with less model complexity, but the applicability of the model needs to be verified.