Study of the viscoplastic behavior of polar ice : deformation modes and texture development simulation

• Main Author: Montagnat, Maurine
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Joseph-Fourier - Grenoble I, Duval Paul([e-mail])
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2001
• Subjects: Glaces polaires. Déformation viscoplastique. Texture. Modèles micro-macro; Polar ice. Viscoplastic deformation. texture. Micro-macro modelling; [SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph]; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Antarc*; Antarctica; ice core; Ice Sheet
• Online Access: https://theses.hal.science/tel-00010695; https://theses.hal.science/tel-00010695/document; https://theses.hal.science/tel-00010695/file/tel-00010695.pdf

The deformation of ice in polar ice sheets implies strain rates lower than 10e-10s-1. The rheology of polar ice is governed by intracrystalline slip and is associated with the occurence of grain growth and dynamic recrystallization. The stress exponent of the secondary creep is lower than 2. A deformation model based on equilibrium between work hardenning and recovery in ice sheet is developed. Hard X-ray diffraction experiments are performed on ice monocrystals taken along the deep Vostok core (Antarctica). The measured lattice distortion can be described by basal geometrically necessary dislocations of screw and edge type. Deformation modes of polar ice are determined by taking into account the mechanical behavior and the arrangement of dislocations. The simulation of the texture development is performed by using the Visco-Plastic Self Consistent (VPSC) "1-site" model developed by Lebensohn and Tomé (1993). This model is modified to take into account the anisotropy of the ice monocrystal, and polar ice deformation conditions. A good estimation of texture development along the Vostok and GRIP ice core is obtained. Expansion of the model to introduce rotation recrystallization does not point out the influence of associated mechanisms on texture development. Finally, a "n-sites" type of modelling using Fast Fourier Transform (Lebensohn 2001) is investigated to simulate the heterogeneities within crystals and improve the calculation of grain interactions. La déformation de la glace des calottes polaires implique des vitesses de déformation inférieures à 10e-10 s-1. La glace se déforme essentiellement par glissement intracristallin auquel sont associés les processus de grossissement normal et de recristallisation dynamique. La loi de fluage se caractérise par un exposant des contraintes inférieur à 2. Les mécanismes physiques qui interviennent au cours de la déformation de la glace polaire sont étudiés par l'intermédiaire d'un modèle physique basé sur l'équilibre écrouissage / restauration. Des expèriences de ...