Haslam, Richard Brooke (2012) 3D geological modelling of superficial deposits, bedrock stratigraphy and fracture networks, Dounreay, Scotland: implications for subsurface contaminant pathways. Doctoral thesis, Keele University.

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Abstract

Any industrial site producing contaminants (including chemical and radiological materials), will be constructed on or below the surface, whose associated properties determine how fluid and contaminants travel. The Dounreay Nuclear Power Establishment offers a unique opportunity to understand bedrock geology, superficial deposits, shallow fractures, and their controls on fluid and contaminant pathways. This is due to its complex history, possible contaminants and extensive prior site investigations.
Three-dimensional geological modelling is becoming an integral part of site investigations as affordable technology becomes more powerful. Using previously collected, data and state-of-the-art modelling, a high-resolution geological model has been created based on understanding the cyclicity of the Devonian sedimentation of the Orcadian Basin. This underlies the site providing a framework for discrete fracture network and stochastic facies modelling. A discrete fracture network, for three fracture sets, has been created for the bedrock geology through statistical analysis of scanline and borehole data, and stochastic simulations of fracture intensity throughout the geological model. Due to the heterogeneity of the superficial deposits, a stochastic simulation was used to interpolate five distinct superficial facies, considered to influence contaminant pathways and identified from geotechnical logs; 1–Clay, 2–Sand, 3–Gravel, 4–Silt and 5–Peat.
Fracture intensity of the hydraulically conductive bedding-parallel fracture set decreases logarithmically with increasing depth. The decreasing fracture intensity of the bedding-parallel fractures reflects a decreasing horizontal hydraulic conductivity, which at 100m levels off and becomes approximately equal to the vertical hydraulic conductivity. The superficial deposits are predominantly clay, with the maximum hydraulic conductivity associated with the gravel facies. The gravel facies provide connectivity from the land surface to the bedrock and associated fracture networks. Methodologies used here can be applied to any site investigation, providing adequate data is available, and by integration, analysis and three-dimensional modelling of the shallow subsurface, a better understanding of contaminant pathways and uncertainties can therefore be achieved.

Item Type: Thesis (Doctoral)
Additional Information: Indefinite embargo
Subjects: Q Science > QE Geology
Divisions: Faculty of Natural Sciences > School of Physical and Geographical Sciences
Depositing User: Lisa Bailey
Date Deposited: 28 Jul 2017 09:42
Last Modified: 28 Jul 2017 09:42
URI: http://eprints.keele.ac.uk/id/eprint/3863

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