Influence of Temperature Variation on Complex-Impedance Measuring Instrument Test Results

A complex-impedance measuring instrument (CIMI) is a relatively new non-nuclear device for measuring unit weight and moisture content of soil for QA/QC testing. The device is more commonly known by its manufacturer trade name, the “electrical density gauge” (EDG). A CIMI uses a series of electrical measurements correlated with measured in situ soil properties to create a soil model to infer in situ soil unit weight and moisture content. From previous research performed investigating the CIMI, the authors have identified that soil temperature influences the electrical measurements recorded by the device, and that the proprietary temperature compensation algorithm provided by the manufacturer does not always improve results. In order to evaluate the effects of temperature on the electrical properties measured by a CIMI, a series of tests under various temperature gradient cycles were performed on soil specimens in large Proctor-type molds, and the electrical properties of the soil were recorded by the CIMI throughout these tests. This study provides a new data set to illustrate how temperature can affect CIMI measurements, which can be useful for developing improved temperature correction algorithms for the CIMI in the future.