Does gravity cause load-bearing bridges in colloidal and granular systems?

Jenkins, M. C. and Haw, M. D. and Barker, G. C. and Poon, W. C. K. and Egelhaaf, S. U. (2011) Does gravity cause load-bearing bridges in colloidal and granular systems? Physical Review Letters, 107 (3). ISSN 0031-9007

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    Abstract

    We study structures which can bear loads, "bridges", in particulate packings. To investigate the relationship between bridges and gravity, we experimentally determine bridge statistics in colloidal packings. We vary the effective magnitude and direction of gravity, volume fraction, and interactions, and find that the bridge size distributions depend only on the mean number of neighbors. We identify a universal distribution, in agreement with simulation results for granulars, suggesting that applied loads merely exploit preexisting bridges, which are inherent in dense packings.