Hydraulic bridges in unsaturated coarse granular media: Influence of bridge size and conductivity on flow through clasts |
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| Institution: | 1. Department of Civil Engineering, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L7, Canada\n;2. School of Geography and Earth Sciences, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L7, Canada\n;1. GeoRessources (UMR 7359, Université de Lorraine / CNRS / CREGU), Vandoeuvre-lès-Nancy, F-54518, France;2. Centre d’Hydrogéologie et de Géothermie, Université de Neuchâtel, 11 rue Emile-Argand, 2000 Neuchâtel, Switzerland;1. UFZ - Helmholtz Centre for Environmental Research, Department Hydrogeology, Permoserstr. 15, 04318 Leipzig, Germany;2. UFZ - Helmholtz Centre for Environmental Research, Department Aquatic Ecosystem Analysis, Brückstr. 3a, 39114 Magdeburg, Germany;3. Institute of Landscape Hydrology, Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Str. 84, 15374 Müncheberg, Germany;4. Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany;5. UFZ - Helmholtz Centre for Environmental Research, Department Catchment Hydrology, Theodor-Lieser-Str. 4, 06120 Halle, Germany |
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| Abstract: | Unsaturated flow in coarse granular media must pass through hydraulic bridges (e.g., pendular water, porous connections) that form a physical connection between adjoining clasts. Previous studies suggest that volumetric flow through a porous clast (Q) will be linearly dependent on the cross-sectional area of the hydraulic bridges, and understate the importance of bridge conductivity. Numerical simulations were performed to explore steady-state flow through a spherical clast with identical bridges located at the top and bottom. The cross-sectional area of the bridges relative to that of the clast (Ar) was varied across six orders of magnitude. The ratio of hydraulic conductivity between bridges and clasts (Kb/Kc) was varied across 12 orders of magnitude to consider resistive, neutral, and conductive bridges. Results show that hydraulic bridges place a primary control on both Q and flux distribution within the clast. For neutral and conductive bridges (Kb/Kc ≥1), Ar is the dominant factor in determining Q, while Kb/Kc is the primary control for resistive bridges (Kb/Kc < 1). For all bridges, Q shows a non-linear dependency on both Ar and Kb/Kc. The intra-clast flow distribution shifts outwards as Ar increases. Conductive bridges promote this process and resistive bridges impede it. |
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