Fundamental Experiments for Measurement of Depth of Frozen Soil using Time Domain Reflectometry

Abstract

The time domain reflectometry (TDR), which has been used for the measurement of volumetric soil water content θ, seems theoretically possible to also be applied for the measurement of the depth of frost penetration (frozen depth). Experiments for locating the interface between frozen and unfrozen soil using the TDR were conducted on two soils, a Toyoura sand and a Masa soil.The samples used in the experiments consisted of frozen-unfrozen soil systems in which the artificially frozen soils were placed on top of the unfrozen soils and both layers were adjusted at the same fixed θ values with distilled water or 2000 ppm NaCl solution.Then the results were compared with those from direct measurements of the frozen depth using a ruler.
In these experiments, the results have shown that the TDR can be used to determine the frozen depth with an average absolute error from values by the direct measurements in the used soils of ≅-0.2 and-≅-0.1within 0.28cm and 0.34cm, respectively, regardless whether the soils are saline or not.These findings seem useful for measurement of the frozen depth in fields.