Book/Dissertation / PhD Thesis

FZJ-2015-06593

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Using the anisotropy of electrical properties for the characterization of sedimentological structures and preferential flow processes

Al-Hazaimay, S. (Corresponding author)FZJ*

2015
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-090-6

Please use a persistent id in citations: http://hdl.handle.net/2128/9521  urn:nbn:de:0001-2016022900

Abstract: Detailed information about subsurface structures (e.g. layering) and processes (e.g. ow and solute transport) in the vadose zone is important for the characterizationand protection of soil and groundwater. Unfortunately, such informationis not easily accessible due to the complexity of the soil system that exhibitsconsiderable spatial variation in subsurface structure, which introduces signifi-cant uncertainty when attempting to improve system understanding. Because oflayering structures and macropores in the subsurface, signiffcant changes in soilproperties appear in horizontal and vertical directions that introduce anisotropyin soil properties such as the hydraulic conductivity and the electrical resistivity.The premise of this thesis is that anisotropy in electrical resistivity can be usedto extract meaningful information about other soil characteristics and properties.In particular, we investigate whether the anisotropy in electrical properties canbe used to obtain information about the heterogeneity of sediment structures andmacropore preferential ow processes using non-invasive geophysical techniquesbecause such information is hard to obtain in feld applications using classicaldestructive methods. Synthetic modelling has shown that information on soil heterogeneity can be obtainedfrom the anisotropy in electrical resistivity. In particular, it was shown thatthe correlation length ratio of bimodal facies distribution of two isotropic materialswith different complex resistivity can be inversely estimated from the effectivecomplex electrical resistivity in two directions (i.e. the anisotropy). In this thesis,this result from a synthetic modelling study was experimentally validated usingcomplex electrical resistivity measurements on a measurement cell with two bimodalsediment distributions that differ in the fraction and spatial arrangementof each material. The effective complex electrical resistivity in the mHz to kHz frequency range of these two sediment distributions was determined using a novelanalysis approach. To estimate the correlation length ratio, we used a global optimization method that minimized the difference between measured and modelled effective electrical resistivity. Effective complex electrical resistivity measurementsof heterogeneous distributions showed a good agreement with the results obtained in the synthetic study for the same distributions, although measurement results were very sensitive to the sample thickness that was difficult to control. It wasconcluded that the electrical anisotropy in resistivity can indeed be used to obtain information about the heterogeneity in sediments with a very high accuracy in correlation length ratio, volume fraction, and the electrical parameters of the Cole-Cole model.

Note: Dissertation, RWTH Aachen, 2015

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Contributing Institute(s):

1. Agrosphäre (IBG-3)

Research Program(s):

1. 255 - Terrestrial Systems: From Observation to Prediction (POF3-255) (POF3-255)

Appears in the scientific report 2015

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Database coverage:

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