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    Volume 43, Issue 4 (July 2020)

    Modified Thermomechanical Triaxial Cell for Microscopic Assessment of Clay Fabric Using Synchrotron X-Ray Diffraction

    (Received 30 January 2019; accepted 24 May 2019)

    Published Online: 19 July 2019

    CODEN: GTJODJ

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    Abstract

    This article presents a thermomechanical triaxial cell modified to fit inside a synchrotron X-ray diffraction (XRD) beamline aiming to assess thermally induced microstructural changes in saturated clays under in situ conditions. Understanding these thermally induced microstructural alternations in clays will explain some of the poorly understood or misunderstood concepts about the thermomechanical behavior of these soils; this, in turn, will allow more robust designs of geostructures for thermal and energy applications. Compared to other techniques, synchrotron diffraction provides (1) high accuracy and sensitivity to small changes compared to benchtop XRD and (2) the ability to assess microstructure changes under in situ conditions (i.e., stress, saturation, and temperature). The design and selection of the various materials used in the modified triaxial cell are first presented. Based on this design, it is recommended to use (1) sample diameters in the 5 to 7–mm range to minimize sample disturbance during trimming and X-ray background scattering during X-ray scans and (2) a transparent cell with acrylic walls, with nitrogen gas as the confining fluid and neoprene membranes, since all considered cell wall materials (i.e., acrylic and aluminum), confining gases (i.e., nitrogen, carbon dioxide, argon, and compressed air), and membrane materials (i.e., latex and neoprene) result in accurate diffraction measurements. The modified cell was then used to assess the changes in particle reorientations of a normally consolidated kaolinite clay after the saturation and consolidation stages as well as the heating load. The results showed that the saturation and consolidation stages reoriented the particles perpendicular to the longitudinal axis of the sample, which is the same direction as the pore water flowing in and out of the sample. Further particle reorientations were observed due to heating.

    Author Information:

    Abdelaziz, Sherif L.
    Department of Civil Engineering, Stony Brook University, Stony Brook, NY

    Jaradat, Karam A.
    Department of Civil Engineering, Stony Brook University, Stony Brook, NY

    Zeinali, Seyed Morteza
    Department of Civil Engineering, Stony Brook University, Stony Brook, NY


    Stock #: GTJ20190036

    ISSN:0149-6115

    DOI: 10.1520/GTJ20190036

    Author
    Title Modified Thermomechanical Triaxial Cell for Microscopic Assessment of Clay Fabric Using Synchrotron X-Ray Diffraction
    Symposium ,
    Committee D18