Sliding friction on wet and dry sand.
We show experimentally that the sliding friction on sand is greatly reduced by the addition of some-but not too much-water. The formation of capillary water bridges increases the shear modulus of the sand, which facilitates the sliding. Too much water, on the other hand, makes the capillary bridges coalesce, resulting in a decrease of the modulus; in this case, we observe that the friction coefficient increases again. Our results, therefore, show that the friction coefficient is directly related to the shear modulus; this has important repercussions for the transport of granular materials. In addition, the polydispersity of the sand is shown to also have a large effect on the friction coefficient.
Van der Waals-Zeeman Institute, IoP, University of Amsterdam, Science Park 904, 1098XH Amsterdam, Netherlands.
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Fall
Van der Waals-Zeeman Institute, IoP, University of Amsterdam, Science Park 904, 1098XH Amsterdam, Netherlands.
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Weber
Van der Waals-Zeeman Institute, IoP, University of Amsterdam, Science Park 904, 1098XH Amsterdam, Netherlands and Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159 Zanjan, Iran.
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Pakpour
Material Imaging, UR Navier, 77420 Champs-sur-Marne, France.
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Lenoir
Van der Waals-Zeeman Institute, IoP, University of Amsterdam, Science Park 904, 1098XH Amsterdam, Netherlands.
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Shahidzadeh
Experimental Physics, Saarland University, D-66123 Saarbrücken, Germany and Gravitation Group, TATA Institute of Fundamental Research, 1 Homi Bhabha Road, 400005 Mumbai, India.
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Fiscina
Experimental Physics, Saarland University, D-66123 Saarbrücken, Germany.
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Wagner
Van der Waals-Zeeman Institute, IoP, University of Amsterdam, Science Park 904, 1098XH Amsterdam, Netherlands.
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Bonn