1 research outputs found
Anomalous density dependence of static friction in sand
We measured experimentally the static friction force on the surface of
a glass rod immersed in dry sand. We observed that is extremely sensitive
to the closeness of packing of grains. A linear increase of the grain-density
yields to an exponentially increasing friction force. We also report on a novel
periodicity of during gradual pulling out of the rod. Our observations
demonstrate the central role of grain bridges and arches in the macroscopic
properties of granular packings.Comment: plain tex, 6 pages, to appear in Phys.Rev.