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The role of in situ stress in determining hydraulic connectivity in a fractured rock aquifer (Australia) |
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| Authors: | Luke Mortimer Adnan Aydin Craig T Simmons Graham Heinson Andrew J Love |
| Institution: | 1. School of the Environment and National Centre for Groundwater Research and Training, Flinders University, G.P.O. Box 2100, Adelaide, South Australia, 5100, Australia 2. Department of Geology and Geological Engineering, University of Mississippi, PO Box 1848, University, MS, 38677, USA 3. School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia, 5005, Australia |
| Abstract: | Fracture network connectivity is a spatially variable property that is difficult to quantify from standard hydrogeological datasets. This critical property is related to the distributions of fracture density, orientation, dimensions, intersections, apertures and roughness. These features that determine the inherent connectivity of a fracture network can be modified by secondary processes including weathering, uplift and unloading and other mechanisms that lead to fracture deformation in response to in situ stress. This study focussed on a fractured rock aquifer in the Clare Valley, South Australia, and found that fracture network connectivity could be discriminated from several geological, geophysical and hydrogeological field datasets at various scales including single well and local- to regional-scale data. Representative hydromechanical models of the field site were not only consistent with field observations but also highlighted the strong influence of in situ stress in determining the distribution of fracture hydraulic apertures and the formation of hydraulic chokes that impede fluid flow. The results of this multi-disciplinary investigation support the notion that the hydraulic conductivity of a fracture network is limited to the least hydraulically conductive interconnected fractures, which imposes a physical limit on the bulk hydraulic conductivity of a fractured rock aquifer. |
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