Influence of temperature and water content of soil on electrical resistivity tomography (ERT)

Abstract

Soil is a dynamic natural body having different properties determined by its origin, modified over time by several geological deformations like glacial rebounds. Several geological and geotechnical techniques have been developed over the years to investigate this dynamic nature of the soil. One of the essential means to study the properties of soils is the Electrical Resistivity Tomography (ERT), which is a non-destructive and inexpensive method of investigation. Although the ERT method provides accurate information on the soil resistivity, the accuracy of the result obtained is however influenced for instance by temperature and water content of the soil. It is common knowledge that the resistivity of soil is affected by its water content and temperature. However, the temperature effect is neglected very often in some ERT studies. Therefore, this thesis concentrates particularly on the effects of the temperature but also water content of the soil on the soil resistivity.

This study involves onsite measurements of soil resistivity while monitoring and measuring the soil water content, temperature, and conductivity at different intervals by TDR probe buried beneath the soil surface. Finally, the resistivity of the soil samples obtained from different locations around Metsähovi and Aalto University, Otaniemi campus are measured under controlled laboratory conditions by varying the soil water content and temperature.

The results obtained in both cases show that the soil resistivity decrease with an increase in soil moisture. However, it seems that the temperature effect on ERT values is higher with lower soil water content and possibly the soil particle size and texture.