LABORATORY MEASUREMENTS OF ELECTRICAL RESISTIVITY VERSUS WATER CONTENT ON SMALL SOIL CORES

The assessment of soil water content variations more and more leans on geophysicalmethods that are non invasive and that allow a high spatial sampling. Among thedifferent methods, DC electrical imaging is moving forward. DC Electrical resistivityshows indeed strong seasonal variations that principally depend on soil water contentvariations. Nevertheless, the widely used Archie’s empirical law [1], that linksresistivity with voids saturation and water conductivity is not well suited to soilmaterials with high clay content. Furthermore, the shrinking and swelling propertiesof soil materials have to be considered. Hence, it is relevant to develop new laboratoryexperiments in order to establish a relation between electrical resistivity and watercontent taking into account the rheological and granulometrical specificities of soilmaterials.The experimental device developed in IRD laboratory allows to monitor simultane-ously (i) the water content, (ii) the electrical resistivity and (iii) the volume of a smallcylindrical soil core (100cm3) put in a temperature controlled incubator (30