A simple test method to measure unfrozen water content in clay-water systems

Object: A simple test method is proposed to measure the unfrozen water content for frozen soils in the laboratory. Method: Three types of soil samples are frozen at a negative temperature first then melted by natural convection. Based on Newton's law of cooling, a mathematical formulation is derived to characterize the variation of the temperature in time domain for the whole process. The important parameters, such as convective heat transfer coefficient, freezing point and length of melting time, are obtained by fitting the temperature-time history recorded in the tests. The unfrozen water content and its characteristic curves are obtained accordingly. Result: The results showed that, at frozen state, the unfrozen water content in the silt, siltyclay and clay is 6.32%, 8.93% and 12.66%, respectively. Probably because of the difference in their properties, the difference of unfrozen water content in these three soils is pronounced. The obtained characteristic curve of unfrozen water content is implemented in the FEM program and a back analysis on melting process is performed. The simulation results show excellent agreement with laboratory measurements. Conclusion: Since the results from theoretical analysis, laboratory experiment and numerical simulation are all consistent with each other, the proposed test method for measuring unfrozen water content seems like a valid approach. (C) 2012 Elsevier B.V. All rights reserved.