Investigating the Complex Resistivity (0.01-1000 Hz) Response to Saturation State for Unconsolidated Sediments

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0073680SlaterThis award supports research on the low frequency (0.1-1000 Hz) electrical properties of unconsolidated, under-saturated sediments. Previous research has identified the value of complex resistivity (CR) measurements for predicting grain size distribution, hydraulic conductivity and hydrocarbon contaminants in saturated media. However, the influence of under-saturation on polarization mechanisms occurring at the grain-fluid interface is not well understood. This work will investigate the CR dependence on degree of saturation and will hence determine its application in hydrogeological and agricultural assessments of the vadose zone. Ground penetrating radar and electrical resistivity methods can provide information on moisture content. The use of CR for providing additional hydrological information, such as capillary potential, pore fluid distribution and hysteresis effects in a drying-wetting cycle, will be determined. This work initiates research in applied electrical geophysics at the University of Missouri, Kansas City. The PI will make measurements of complex resistivity, degree of saturation and capillary potential on a range of unconsolidated sediments during a cycle of drainage and wetting. Important structural parameters, including grain size distribution, specific surface area, porosity, true formation factor and mineralogy will be evaluated for all samples. As structural properties control the surface area over which polarization acts, the CR response to saturation is expected to vary considerably for the range of unconsolidated sediments investigated.***