Microstructural Interpretation of Water Content and Dry Density Influence on the DC-Electrical Resistivity of a Fine-Grained Soil

    Volume 34, Issue 6 (November 2011)

    ISSN: 0149-6115

    CODEN: GTJOAD

    Published Online: 11 July 2011

    Page Count: 14


    Beck, Yves-Laurent
    Département Surveillance Eau et Ouvrage, Service Développement, Matériel, Méthode,

    Palma Lopes, Sérgio
    PRES Université Nantes Angers Le Mans,

    Ferber, Valéry

    Côte, Philippe
    PRES Université Nantes Angers Le Mans,

    (Received 10 January 2011; accepted 17 May 2011)

    Abstract

    In geotechnical engineering, there is a need for an in situ technique for measuring density and water content of soils quickly, accurately and, preferably, in a non-destructive way. DC-electrical resistivity provides a method capable of addressing this need. A new resistivity-cell and a new experimental procedure were developed to assess the resistivity of compacted samples of a silty soil. The study was carried out over moisture content and compaction level ranges that are consistent with those acceptable in earthwork construction. In this laboratory work, the effects of dry density and gravimetric water content on the soil bulk resistivity are considered separately. Furthermore, the effect of air index on electrical resistivity is demonstrated. Our data exhibit two distinct trends separated by a “critical” water content which appears to fall very close to the standard Proctor optimum moisture content for this soil. This promising result cannot be generalized as it needs to be investigated on other soils. The experimental results are further analyzed within the context of a previously published soil microfabric model which distinguishes water phase, air phase, particles assumed to be “inert” and clayey aggregates. Two types of electrical conduction enable explaining the results: first, conduction occurring in the intra-aggregate voids, controlled by the charge density on the surface of clayey particles; and then, inter-aggregate conduction controlled by interstitial water resistivity. The relative effect of each type of conduction is shown to strongly depend on water content. Finally, an extrapolation at zero air void allows for presenting an interpretation of the intra-aggregate volume contribution to electrical conduction in dry states. This interpretation suggests a dilution effect on the adsorbed cation concentration within bound water, that is shown to be consistent with recently published research.


    Paper ID: GTJ103763

    DOI: 10.1520/GTJ103763

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    Author
    Title Microstructural Interpretation of Water Content and Dry Density Influence on the DC-Electrical Resistivity of a Fine-Grained Soil
    Symposium , 0000-00-00
    Committee D18