Pre-avalanche structural rearrangements in the bulk of granular medium: Experimental evidenceV. Yu. Zaitsev1, P. Richard2, R. Delannay2, V. Tournat3 and V. E. Gusev3
1 Institute Applied Physics, Russian Academy of Sciences - Uljanova St. 46, 603950, Nizhny Novgorod, Russia
2 Institut de Physique de Rennes - UMR CNRS 6251, Université Rennes-1 - 263 av. Général Leclerc, 35042, Rennes Cedex, France, EU
3 LAUM, LPEC, CNRS, Université du Maine - av. Olivier Messiaen, 72085, Le Mans Cedex 9, France, EU
received 28 April 2008; accepted in final form 31 July 2008; published September 2008
published online 10 September 2008
Granular avalanches are typical threshold-type phenomena implying the loss of stability of granular packings when their slope exceeds a critical angle. Detection of avalanche precursors is important for both basic studies and numerous applications. In this respect, only surface observations are presently available, whereas other known techniques are not suitable to detect internal pre-avalanche rearrangements expected from physical considerations and numerical simulations. Here, we report the first experimental evidence of avalanche precursors and the long-lasting post-avalanche rearrangements in the bulk of 3D granular packings. We use an original nonlinear-acoustic probing methodology which is selectively sensitive to the state of weakest intergrain contacts. This methodology allowed us to clearly detect transient pre-avalanche rearrangements of the weak-contact network. Those rearrangements get stronger and exhibit quasi-periodicity closer to the avalanche triggering, whereas the statistics of the sounding signal amplitude shows clear transition from Gaussian to power law behavior.
45.70.Ht - Avalanches.
43.25.+y - Nonlinear acoustics.
83.80.Fg - Granular solids.
© EPLA 2008