Université de Rennes 1, France
Posters & Accepted Abstracts: J Phys Chem Biophys
Exploration of the dynamical response of an inclined granular packing brings information which may be helpful for the prediction of the occurrence of the avalanche. During inclination, small rearrangements implying only a few grains are first detected. Their size increases with the inclination angle. At some stage, large amplitude and quasi periodical events are observed . These events, called precursors, consist of collective motions of grains. Experiments showed that the precursors are bulk phenomena and allowed to interpret these events as reorganizations of the weak-contact sub network occurring in the packing. Besides optical imaging techniques which give access to grain motion and rearrangements during the tilting, acoustic methods can be experimentally used to detect precursors and to probe internal rearrangements in the bulk of the granular layer. Because part of the acoustic wave energy transports through the contact network and the elastic beads of the medium, the probing methods based on the monitoring of acoustic signatures are sensitive to changes in the elastic properties of the granular layer. The acoustic probing methods can be divided in two groups, the passive methods where acoustic sensors are used to listen to the sounds emitted by the destabilized layer itself and the active methods where an acoustic signal with desired properties is generated and detected by transducers in the medium. Systematic experiments of granular layer destabilization for various granular media and external conditions are compared and allow better understanding of the mechanisms responsible for the appearance, periodicity and intensity of precursors.
Email: [email protected]