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    Volume 40, Issue 4 (July 2017)

    Integrating the Four-Probe Method and SWCC Device to Measure Electrical Resistivity Anisotropy of Unsaturated Soil

    (Received 12 July 2016; accepted 23 January 2017)

    Published Online: 2017

    CODEN: GTJODJ

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    Abstract

    Electrical resistivity is often utilized to estimate different flow-related properties of unsaturated soils, such as hydraulic conductivity. To be better utilized for such a purpose, the electrical resistivity anisotropy has to be characterized to account for the anisotropic nature of soils. Thus, a testing cell equipped with two individual four-probe arrays was designed and manufactured using the 3D printing technique. The testing cell was integrated with a soil water characteristic curve (SWCC) device, and therefore both the soil resistivity anisotropy and SWCC could be measured simultaneously in the same sample. Numerical simulations using the finite element method (FEM) were carried out to characterize the measurement biases due to the boundary effect from the finite sample size and the influence of the electrode sizes, and then to determine the associated correction factors. The validity of the correction factors was also experimentally verified. Experimental results on the mica samples reveal that the electrical resistivity in the vertical and horizontal directions (i.e., ρV and ρH) increases as the suction increases or the degree of saturation decreases. In addition, the anisotropic factor, λ = √ρV/ρH, was found to gradually increase with increasing suction or decreasing water content.


    Author Information:

    Wu, Y.
    Dept. of Civil and Environmental Engineering, The Hong Kong Univ. of Science and Technology, HKSAR,

    Wang, Y. H.
    Dept. of Civil and Environmental Engineering, The Hong Kong Univ. of Science and Technology, HKSAR,

    Niu, Q.
    Dept. of Geology, The Univ. of Kansas, Lawrence, KS


    Stock #: GTJ20160160

    ISSN:0149-6115

    DOI: 10.1520/GTJ20160160

    Author
    Title Integrating the Four-Probe Method and SWCC Device to Measure Electrical Resistivity Anisotropy of Unsaturated Soil
    Symposium ,
    Committee D18