MICROSTRUCTURAL CHANGES ASSOCIATED WITH THIXOTROPIC PHENOMENA IN CLAY SOILS

Thixotropic phenomena in clay soils are accompanied by microstructural changes. The nature of these changes is unclear because of the short duration of the thixotropic processes and the difficulties involved in preparing a specimen at certain stages. However, these technological problems were overcome and scanning electron microscope photographs were obtained of the thixotropic soil microstructure during deformation of samples in a rotary viscometer with and without vibration. The new data obtained clarify the mechanism of thixotropic phenomena. Soil microstructure was not ruptured by vibration during the shear process. On the contrary, it became more homogeneous over the entire volume and at the same time this induced a decrease in strength in the system due to a reduction in cohesion at contacts. Disruption of some structural bonds is followed by their rapid restoration -the overall microstructure remaining intact. As a result, in all the samples studied the shear zone disappears. In kaolinite clay and coarser dispersed soils (silty clay, water-saturated loess) the local areas of the structural framework (shear planes) become smoother and the orientation of the structural elements along the direction of shear disappears. After the cessation of vibration, the microstructure is rapidly restored to its initial state. (Author/TRRL)

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: p. 293-303
  • Serial:
    • GEOTECHNIQUE
    • Volume: 34
    • Issue Number: 3
    • Publisher: Thomas Telford Limited
    • ISSN: 0016-8505

Subject/Index Terms

Filing Info

  • Accession Number: 00394628
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: Jul 31 1985 12:00AM