This paper describes a comparison study on three different technologies (i.e., thermocouple, electrical resistivity probe and Time Domain Reflectometry (TDR)) that are commonly used for frost measurement. Specially, the paper developed an analyses procedure to estimate the freezing-thawing status based on the dielectric properties of freezing soil. Experiments were conducted where the data of temperature, electrical resistivity, and dielectric constant were simultaneously monitored during the freezing/thawing process. The comparison uncovered the advantages and limitations of these technologies for frost measurement. The experimental results indicated that TDR measured soil dielectric constant clearly indicates the different stages of the freezing/thawing process. Analyses method was developed to determine not only the onset of freezing or thawing, but also the extent of their development. This is a major advantage of TDR over other technologies. 1. Introduction In cold regions, freeze-thaw cycles induce ground settlement and cause the loss of load bearing capacity of subgrades. Soils can be very strong when they are frozen during the winter but become substantially weak in the spring when they are thawing [1]. This leads to large deflection and accelerates crack initialization in pavement structure. In addition to the detrimental effects on soil mechanical properties, freeze-thaw cycles can also affect the subsurface drainage capability and produce additional soil pressure on the underground structures [2, 3]. While extensive research have been conducted on completely frozen soils, the current knowledge on soil behaviors during the freezing-thawing process is limited. For example, Spaans and Baker [4] evaluated the use of TDR in the context of freezing and thawing of soils based on a gas dilatomer calibration. Fen-Chong et al. [5] and Fabbri et al. [6] suggested an empirical method to estimate the degree of freezing in porous media based on permittivity. A few factors could have contributed to the lack of development in this area. This includes, for example, the requirements of sophisticate experimental control to ensure uniform freezing/thawing development; the technical challenge of accurately determining the extent of freezing/thawing in soils. Technologies commonly used for field frost measurement do not provide quantitative data on the extent of soil freezing-thawing. This paper describes a comparison study on frost measurement principles, including those based on the electrical resisitivity, the temperature and the dielectric properties. An
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