Phénomènes collectifs dans les matériaux granulaires. Ecoulements de surface et réarrangements internes dans des empilements modèles

Abstract : Granular media exhibit non-intuitive rheological and mechanical properties. They can flow as liquids but, under specific conditions, they can jam and resist to external stress without shearing. In this thesis, the solid/liquid duality is investigated through two experiments whose main feature is to allow comparisons between the individual behaviour of beads and the one of the packing. The first part of the thesis is devoted to surface flows in inclined packings. A continuous description based on depth averaged conservation equations (Saint-Venant approach) is first derived from the study of steady surface flows in a rotating drum. We then focus on the internal rheology of these flows and investigate spatial correlation of the instantaneous velocity field and the fluctuations of the volume fraction. We demonstrate the existence of rigid clusters of grains embedded in the flows. Their size is power-law distributed from the grain size scale up to the thickness of the flowing layer. The implications of the absence of a characteristic length scale for available theoretical models of dense granular flows are discussed. The second part of the thesis deals with internal rearrangements in packings submitted to a small perturbation. Small thermal variations lead to giant electrical fluctuations in a pile of metallic beads. Statistical analysis of these fluctuations allows us to relate this electrical sensitivity to local tribological fluctuations rather than collective reorganizations of the contact network as proposed in the past. We then visualize the grain micro-displacements entailed by adding a small overload to the surface. This experiment allows us to discuss the validity of the different approaches proposed to describe stress distribution in static packings.
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-00003916
Contributor : Marc Gingold <>
Submitted on : Friday, December 5, 2003 - 5:24:39 PM
Last modification on : Wednesday, January 23, 2019 - 2:38:19 PM
Long-term archiving on : Friday, April 2, 2010 - 7:26:27 PM

Identifiers

  • HAL Id : tel-00003916, version 1

Collections

Citation

Daniel Bonamy. Phénomènes collectifs dans les matériaux granulaires. Ecoulements de surface et réarrangements internes dans des empilements modèles. Analyse de données, Statistiques et Probabilités [physics.data-an]. Université Paris Sud - Paris XI, 2001. Français. ⟨tel-00003916⟩

Share

Metrics

Record views

314

Files downloads

297