HR: 17:45h
AN: T14B-08    [Abstracts]
TI: Damage Models With Porosity and Grainsize Evolution
AU: * Ricard, Y
EM: ricard@ens-lyon.fr
AF: Yanick Ricard, Universite de Lyon bat Geode 2 rue R. Dubois, Villeurbanne, 69622 France
AU: Bercovici, D
EM: david.bercovici@yale.edu
AF: David Bercovici, Dpt Geology and Geophysics Yale University, New Haven, CT 06511 United States
AB: The process of localization in a deforming solid is related to a dynamic feedback between the deformation itself and the rheology controlled by macroscopic (pressure, temperature) and microscopic (grain size average and distribution, porosity) variables. In this contribution, using simply the most fundamental thermodynamic requirements (energy conservation and positivity of entropy production) we constrain the relationships between the evolution of grain size and/or porosity with deformation. This approach provides various models of damage and we explore the possibilities of localization by porosity increase, average grain size reduction, and evolution of the grain size distribution. The localization of deformation by porosity increase is found to be poorer to generate strike slip motions in 3D settings than the localization by grain-size reduction. Our most complex model considers the case of a continuous grained solid. It couples a microscopic model for the evolution of grain size distribution under deformation to a macroscopic continuum approach for the deformation itself. The kinetics of individual grain size growth is controlled by a balance between local and averaged free energies (that include contributions from grain surface and volume energies as well as from larger scale deformational work). This model predicts the ripening of grains when no deformations are applied (i.e. the healing of a damaged matrix) by generalizing the Lifshitz-Slyozov theory. This model, however is also able to predict the grain size reduction during deformation and localization. We will discuss the possible grain size distributions and modes that can be analytically predicted in simple cases with more complex numerical simulations.
DE: 5100 PHYSICAL PROPERTIES OF ROCKS
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8160 Rheology: general (1236, 8032)
SC: Tectonophysics [T]
MN: Fall Meeting 2005