Eur. Phys. J. E (2011) 34: 65
https://doi.org/10.1140/epje/i2011-11065-0

Permeability of mixed soft and hard granular material: Hydrogels as drainage modifiers

¹ Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, 19104, USA
² Complex Assemblies of Soft Matter, CNRS-Rhodia-UPenn UMI 3254, Bristol, PA, 19007, USA

^* e-mail: emilie.verneuil@espci.fr

Received: 18 March 2011
Accepted: 15 June 2011
Published online: 11 July 2011

Abstract

We measure the flow of water through mixed packings of glass spheres and soft swellable hydrogel grains, at constant sample volume. Permeability values are obtained at constant sample volume and at porosities smaller than random close packing, for different glass bead diameters D and for variable gel grain diameter d, as controlled by the salinity of the water. The gel content is also varied. We find that the permeability decays exponentially in n(D/d ) ^b , where n = N _gel/N _glass is the gel to glass bead number ratio and b is approximately 3. Therefore, flow properties are determined by the volume fraction of gel beads. A simple model based on the porosity of overlapping spheres is used to account for these observations.