Citation
A. Kabla, G. Debregeas, J.-M. di Meglio and T. Senden
EuroPhysics Letter 71:932 (2005)
Abstract
Abstract
An X-ray imaging technique is used to probe the stability of 3-dimensional granular packs in a slowly rotating drum. Well before the surface reaches the avalanche angle, we observe intermittent plastic events associated with collective rearrangements of the grains located in the vicinity of the free surface. The energy released by these discrete events grows as the system approaches the avalanche threshold. By testing various preparation methods, we show that the pre-avalanche dynamics is not solely controlled by the difference between the free surface inclination and the avalanche angle. As a consequence, the measure of the pre-avalanche dynamics is unlikely to serve as a tool for predicting macroscopic avalanches.
Figure sample
Measurement of the dynamics induced by a tilt increment for the system I (see table I): a) radiography of the drum; (b) picture presenting the variations of the crossed grains length ∆L g , at an angle 20◦ ; (c) and (d) measurements of the quadratic fluctuations as a function of the drum angular position θ, respectively for the systems I and II. The thin black line corresponds to a single run, whereas the thick (red online) line shows the average over 15 runs. The data have been rescaled by the average of Q in the avalanche regime.
