Application of the electrical impedance spectrometry method for monitoring of water flow through unsaturated soil

Abstract

Aim of the study: The aim of the research was to determine the sensitivity of the impedance spectrometry (EIS) method to changes in electrical resistance of the soil medium caused by water infiltration. Material and methods: The research was carried out for two mineral soils medium sand and coarse silty sand. The research included determination of basic geotechnical properties of both soils (filtration coefficient, retention characteristic) and water infiltration tests in a vertical soil column. These tests included measurements of changes in electrical resistance of the soil medium, which were compared with the observations of the location of the wetting front and numerical calculations of water flow through the soil. Infiltration tests were done for three soil samples (the first - medium sand, the second - coarse silty sand, the third - medium sand in the bottom and coarse silty sand in top). Results and conclusions: The results of the conducted tests of electrical resistance of soils subjected to the infiltration process in the vertical column confirmed the significant effect of the presence of water in the soil on its electrical resistance. It has been shown that the change in soil moisture content from the air-dry state to full saturation results in the reduction of soil resistance by almost three orders of magnitude. The test results showed a relatively good convergence between the observed position of the wetting front and the measured values of the soil resistance thus confirming the usefulness of the tested measurement method for the monitoring of the water circulation within the soil medium.

Keywords

• soil
• infiltration
• electrical impedance spectrometry