Microscopy Techniques for Viewing the Inner Structure of Shear Bands in Sensitive Clays: Fid-Bau Portal

Microscopy Techniques for Viewing the Inner Structure of Shear Bands in Sensitive Clays

Samstad Gylland, A

Sample preparation and imaging techniques were evaluated for the investigation of fabric and the structures of shear bands in sensitive clays. This included the preparation of polished thin sections, which were studied in a polarized light microscope and in an electron probe micro-analyzer (EPMA). In addition, a set of samples was investigated by X-ray micro-Computerized Tomography, micro-CT. The shear band was seen as a non-continuous displacement field with complex inner patterns of shear fractures, like Riedel shears. Light microscopy of the thin sections was found to be useful for studying the outline and distribution of Riedel shears in the millimeter-sized shear band, whereas EPMA allows for studying microstructures at the micrometer level. The micro-CT makes it possible to extend the 2D representation of the studied macro-features from EPMA and light microscopy into 3D space. The main challenge with sensitive clays is sample preparation; the material can take little or no handling in its wet state, and when dried, substantial shrinkage occurs. The micro-CT holds several strong advantages which overcome these issues and also adds 3D visualization. Despite challenges related to image processing and image resolution versus sample size, the CT-tool is preferred for future studies of shear features in sensitive clays.