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MODELISATION DE L'ECOULEMENT DE LA GLACE POLAIRE ANISOTROPE ET PREMIERES APPLICATIONS AU FORAGE DE DOME C

Abstract : The ice crystal is one of the most anisotropic natural materials. Observations of polar ice show that the crystals are orientated along very marked privileged directions and that the fabric of the ice polycristal is the result of the strain history that the polycristal has undergone. The macroscopic polycristal behaviour depends on the fabric and can be strongly anisotropic. It has been shown that anisotropy can introduce the occurrence of stratigraphy disturbances and influences strongly the flow of the ice sheet.
The aim of this work is to build an ice flow model for anisotropic ice and the evolution of its fabric.
To this end, we model the ice monocrystal as a transversely isotropic continuous medium around its c-axis and we compare it with a slip-planes grain model. The ice fabric is described in a continuous way by the second order orientation tensor and a closure approximation for the fourth ordre orientation tensor. By homogenization, assuming uniform stresses or strain-rates, we obtain analytical solutions for the polycrystal behaviour and the evolution of its fabric. From these solutions, we derive a linear orthotropic flow law for the ice polycrystal and an equation for the evolution of the second order orientation tensor. These equations are able to reproduce the results of the self-consistent model using a discrete fabric description, with an important improvement as regards the computing time and the number of variables necessary to describe the fabric.
These equations are then implemented in a finite element code, used for simulating the flow of an ice sheet with strain-induced evolving anisotropy. By performing synthetic tests, we show the influence of anisotropy on the ice flow. Finally, through our model results, we propose an interpretation of the Dome-C ice-core fabric data.
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https://tel.archives-ouvertes.fr/tel-00125476
Contributor : Fabien Gillet-Chaulet <>
Submitted on : Friday, January 19, 2007 - 5:00:14 PM
Last modification on : Wednesday, October 14, 2020 - 4:09:44 AM
Long-term archiving on: : Tuesday, April 6, 2010 - 10:19:11 PM

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  • HAL Id : tel-00125476, version 1

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Fabien Gillet-Chaulet. MODELISATION DE L'ECOULEMENT DE LA GLACE POLAIRE ANISOTROPE ET PREMIERES APPLICATIONS AU FORAGE DE DOME C. Mécanique [physics.med-ph]. Université Joseph-Fourier - Grenoble I, 2006. Français. ⟨tel-00125476⟩

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