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TRANSITIONS ET COEXISTENCE SOLIDE-LIQUIDE DANS LES MATERIAUX GRANULAIRES

Abstract : To better characterize destabilization, stopping and solid-liquid coexistence mechanisms, experiments and discrete simulations are performed on simple granular piles. Three issues were adressed during this PhD.
The experimental study of the stopping transition of a pile after a surface flow shows long timescales, compared with the typical relaxation time of one grain under its weight. Two coexisting dynamics are observed during the stopping transition : Exponential relaxation periods and reactivation bursts consisting in spatially correlated grains displacements are observed, and taken into account within a probabilistic framework.
The numerical study of a pile inclined below the avalanche angle shows the influence of the metastable domain –above the angle of repose– on its hysteretic response to quasi-static cyclic rotations. The weak contacts network is strongly affected by the exploration of the metastable domain. Correlations between micro-structure, stress and strain variables are discussed.
Finally, unconfined granular flows over a rough incline allow to study experimentally the effective flow rule when static and flowing matter coexist. The selected characteristics (height, width, velocity) evolve logarithmically with time. The consideration of a static basal layer achieves to describe the experimental correlation between flowing depth and surface velocity, as observed for a confined flow, and to predict deposit morphologies (presence or not of levées).
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Submitted on : Monday, January 7, 2008 - 12:06:37 PM
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  • HAL Id : tel-00202523, version 1

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Stéphanie Deboeuf. TRANSITIONS ET COEXISTENCE SOLIDE-LIQUIDE DANS LES MATERIAUX GRANULAIRES. Dynamique des Fluides [physics.flu-dyn]. Institut de physique du globe de paris - IPGP, 2005. Français. ⟨tel-00202523⟩

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