Electrical Resistivity Relation with Clays Water Content and Density

Physical properties of clays are frequently measured in geotechnical engineering because the soft clays constitute an important part of soil foundations for infrastructure development. soil can be easily sampled from a borehole, brought to the laboratory and then evaluated by various geotechnical tests. Soft clays are an absorbent material for some geophysical signals such as seismic and radar signals. This fact partly explains why so far they have not been a favourite target of geophysical investigation (Giao et al., 2003). In most earth materials, porosity and chemical content of water filling the pore spaces are more important in governing resistivity than is the conductivity of mineral grains of which the material itself is composed (Dobrin and Savit, 1998). Electrical conduction in clean sands and gravels occurs primarily in liquid contained in the pores. In clayey soils and clay-bearing rocks, however, electrical conduction occurs in the pores and on the surfaces of electrically charged clay particles. For clays, surface conductance can be a significant factor affecting the bulk electrical resistivity of the soil. Thus, for clays, clay-rich soils, and clay-rich rocks, parallel resistor models were developed to account for conduction through the pore fluid and along the particle surfaces (Abu-Hassanein, 1996). Electric resistivity can be used to characterize the soil properties, but in the same time, it is not a very simple and straightforward parameter like other geotechnical parameters such as water content, liquid and plastic limits and unit weight. Electric resistivity shows no definitive relationship with density (Giao et al. 2003). The application of electrical resistivity for characterization of soil was reviewed by Samouëlian et al. (2005).