Hydraulic Units Associated with Unconsolidated Sediments and Spectral Electrical Response Measurements.

Knowledge of the hydraulic properties of unconsolidated materials (hydraulic conductivity, porosity) from non-invasive geophysical measurements is appealing to geoscientists involved in the hydrological characterization of the earth's subsurface. There is the need to understand the quantitative relationship between measurable geophysical attributes and hydraulic parameters of sediments or soils. Clustering sediments in hydraulic units help in relating parameters characterizing spectral electrical response (SER) measurements and hydraulic conductivity. The SER of soils is modeled with a multi-Cole-cole model considering soils as a heterogeneous multi-phase system. The validity and usefulness of the relations between the electrical parameters and the hydraulic units were assessed using laboratory measurements of the spectral electrical response(0.01Hz to 10 kHz) of over 30 soil samples with wide variability in physical properties. The soils are fully characterized: hydraulic conductivity, porosity, grain size distribution and moisture content of each soil sample were measured. The SER measurements are utilized to estimate the hydraulic unit characterizing the potential flow zones the soils. The intrinsic parameters, which describe the response of the model are retrieved by inversion schemes and are used in establishing the relations. Such relationships between parameters characterizing the spectral electrical response of soils and their hydraulic units may provide versatile and relaible non-invasive methodology of obtaining hydraulic properties information of soils from geophysical measurements.