The use of X-ray computed tomography in the investigation of the settlement behaviour of compacted mudrock
M. A. O'Neill, A. K. Goodwin, W. F. Anderson, 2003. "The use of X-ray computed tomography in the investigation of the settlement behaviour of compacted mudrock", Applications of X-ray Computed Tomography in the Geosciences, F. Mees, R. Swennen, M. Van Geet, P. Jacobs
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The material used in the restoration of opencast coal mines is made up predominantly of mudstone particles ranging in size from less than 60 μm to more than 60 mm nominal diameter. Post-compaction settlements are mainly sub-divided into short-term 'collapse' and long term 'creep' components, both of which can be very large and often significantly reduce the development potential of restored opencast sites. As the mechanics of these movements are poorly understood at present, X-ray computed tomography (CT) was used to investigate the fundamental nature of particulate interactions within specimens of backfill undergoing long-term creep settlement.
The preliminary results from a series of CT analyses of a number of large scale specimens are presented. Different CT procedures were used and an indication for best practice for scanning of large samples has been found. Qualitative interpretation of the images obtained to date is presented in terms of fill structure, particulate changes during settlement and effects of arching. Indications are that particle breakage is a less significant mechanism than previously thought, and that local collapse of voids, particle sliding and particle rotation are the dominant mechanisms. Quantitative data to be extracted from the images may lead to a probabilistic approach to the prediction of settlement. This possibility is noted, as is the potential for the wider use of CT in geotechnical engineering.
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X-ray computed tomography (CT) is a technique that allows non-destructive imaging and quantification of internal features of objects. It was originally developed as a medical imaging technique, but it is now also becoming widely used for the study of materials in engineering and the geosciences. X-ray CT reveals differences in density and atomic composition and can therefore be used for the study of porosity, the relative distribution of contrasting solid phases and the penetration of injected solutions. As a non-destructive technique, it is ideally suited for monitoring of processes, such as the movement of solutions and the behaviour of materials under compression. Because large numbers of parallel two-dimensional cross-sections can be obtained, three-dimensional representations of selected features can be created. In this book, various applications of X-ray CT in the geosciences are illustrated by papers covering a wide range of disciplines, including petrology, soil science, petroleum geology, geomechanics and sedimentology.