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Morphological clues to wet granular pile stability

Nature Materials volume 7, pages 189193 (2008) | Download Citation

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Abstract

When a granular material such as sand is mixed with a certain amount of liquid, the surface tension of the latter bestows considerable stiffness to the material, which enables, for example, sand castles to be sculpted1,2,3,4. The geometry of the liquid interface within the granular pile is of extraordinary complexity and strongly varies with the liquid content5,6,7. Surprisingly, the mechanical properties of the pile are largely independent of the amount of liquid2,8,9,10,11,12,13 over a wide range14,15,16. We resolve this puzzle with the help of X-ray microtomography, showing that the remarkable insensitivity of the mechanical properties to the liquid content is due to the particular organization of the liquid in the pile into open structures. For spherical grains, a simple geometric rule is established, which relates the macroscopic properties to the internal liquid morphologies. We present evidence that this concept is also valid for systems with non-spherical grains. Hence, our results provide new insight towards understanding the complex physics of a large variety of wet granular systems including land slides, as well as mixing and agglomeration problems.

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Acknowledgements

The authors thank K. Mecke and K. Jacobs for valuable discussions. Support from the European Synchrotron Radiation Facility is gratefully acknowledged. We appreciate financial support from the DFG under grant Me1361/9 and within the SFB 755. The authors are indebted to Z. Khan and F. v. Bussel for critical reading of the manuscript.

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Affiliations

  1. Max Planck Institute for Dynamics and Self-Organization, Bunsenstr. 10, D-37073 Göttingen, Germany

    • M. Scheel
    • , R. Seemann
    • , M. Brinkmann
    •  & S. Herminghaus
  2. European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France

    • M. Di Michiel
  3. Dept. Appl. Math., Australian National University, Canberra ACT 0200, Australia

    • A. Sheppard
  4. Institut für Theoretische Physik, Universität Erlangen-Nürnberg, Staudtstrasse 7, D-91058 Erlangen, Germany

    • B. Breidenbach

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Contributions

Experiments were carried out by M.S., R.S., M.DM. and S.H.; theory is by M.B. and S.H.; data analysis was done by M.S., R.S. and M.B.; numerical algorithms and implementation are by A.S. and B.B.

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Correspondence to S. Herminghaus.

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DOI

https://doi.org/10.1038/nmat2117

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