X-ray Computed Tomography Investigation of Structures in Opalinus Clay from Large Scale to Small Scale after Mechanical Testing

Abstract

Abstract. In the past years X-ray Computed Tomography (CT) has became more and more common for geoscientific applications and is used from the µm-scale (e.g. for investigations of micro-fossils or pore scale structures) up to the dm-scale (full drill cores or soil columns). In this paper we present results from CT imaging and mineralogical investigations of an Opalinus Clay core on different scales and different regions of interest, emphasizing especially upon the 3D evaluation and distribution of cracks and their impact upon mechanical testing of such material. Enhanced knowledge of the testing behavior of the Opalinus Clay is of great interest, especially since this material is considered for a long term radioactive waste disposal and storage facility in Switzerland. Hence, results are compared regarding the mineral (i.e. phase) contrast resolution, the spatial resolution, and the overall scanning speed. With this extensive interdisciplinary top-down approach it has been possible to characterize the general fracture propagation in comparison to mineralogical and textural features of the Opalinus Clay. Additionally, and as far as we know, a so called mylonitic zone, located at the intersect of two main fractures, has been observed for the first time for an experimentally deformed Opalinus sample. The multi-scale results are in good accordance to data from naturally deformed Opalinus Clay samples, which enables to perform systematical research under controlled laboratory conditions. Accompanying 3D imaging greatly enhances the capability of data interpretation and assessment of such a material.

Pore-scale tomography and imaging: applications, techniques and recommended practice

“…Within the paper of Schoesser et al (2016), research of the penetration behavior of bentonite suspensions into noncohesive media is presented. Saenger et al (2016) present recommendations for digital carbonate rock physics performed on imaging data sets, and Kaufhold et al (2016) investigated structures in Opalinus Clay on multiple scales after mechanical testing for the long-term storage of radioactive waste. Kling et al (2016) showcase a new approach of fluid flow modeling in fractured rocks, whereas Grathoff et al (2016) modeled porosity and permeability of organic-rich Posidonia shales from FIB-SEM data sets.…”

X-ray Computed Tomography of Structures in Opalinus Clay from Large Scale to Small Scale after Mechanical Testing

“…In this study we present the investigations of an experimentally deformed Opalinus Clay (OPA, Kaufhold et al, 2016). The aim is the visualization of the shear failure at various scales to get more information about the deformation process.…”