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Étude numérique du cisaillement des géomatériaux granulaires cohésifs : passage micro-macro, microstructure, et application à la modélisation de glissements de terrain

Abstract : The present PhD thesis is devoted to the numerical simulation and analysis of shear on cohesive granular materials. In the framework of the Contact Dynamics method, we developed a model of cohesive bonding, which mimics cohesion by cementation. This model involves three contact strength parameters (a tensile strength, a coefficient of sliding friction, and a coefficient of rolling friction) as well as a local criterion, which controls the creation and the breaking of cohesive bonds. All contacts are cohesive at the beginning of the numerical simulations, and contact rupture leads to an irreversible loss of tensile strength (debonding). We varied systematically the three contact strength parameters and studied their influence on the shear strength, the dilatancy, and the microstructure of the granular media. Our results show that internal friction and macroscopic tensile strength have different origins at the contact scale. We also find that the microstructure of the granular media, when sheared at the steady state (also known as the `critical state"), is strongly affected by the local coefficients of sliding and rolling friction. In particular, the mechanical role of the weak network changes with these two contact parameters, which results from the formation of a new structure of force transmission. On the other hand, we also applied the same numerical simulation method to the simulation of landslides. We developed a methodology, which takes into account the initial morphology of the hillslope, the strength of geomaterials, and a triggering factor, integrating in the same model the initiation and propagation phases of the landslide. To illustrate this methodology, we applied it to the simulation of a hypothetical example of avalanche triggered by the progressive rise of a water table.
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Contributor : Nicolás Estrada Mejía <>
Submitted on : Wednesday, August 13, 2008 - 9:15:53 PM
Last modification on : Friday, April 5, 2019 - 8:14:36 PM
Long-term archiving on: : Thursday, June 3, 2010 - 6:21:03 PM

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Nicolás Estrada Mejía. Étude numérique du cisaillement des géomatériaux granulaires cohésifs : passage micro-macro, microstructure, et application à la modélisation de glissements de terrain. Mécanique [physics.med-ph]. Université Montpellier II - Sciences et Techniques du Languedoc, 2008. Français. ⟨tel-00311303⟩

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