HR: 14:10h
AN: T43E-03 INVITED    [Abstracts]
TI: Fragmentation and Localization Processes in 3D Simulations of Sheared Granular Systems
AU: * Mair, K
EM: karen.mair@fys.uio.no
AF: Physics of Geological Processes, University of Oslo, PO box 1048, Blindern, Oslo, 0316, Norway
AU: Abe, S
EM: s.abe@ged.rwth-aachen.de
AF: Geologie-Endogene Dynamik, RWTH Aachen, Lochnerstrasse 4-20, Aachen, 52056, Germany
AB: To better understand deformation processes relevant for sediments and sedimentary rocks, we investigate the grain scale processes operating in evolving granular systems under shear. Structural fabrics, such as deformation bands, are common in nature however the micro-scale processes responsible for their development are generally difficult to directly observe. Discrete numerical models of granular systems allow excellent visualization of grain scale interactions as well as tracking of macroscopic mechanical response. When combined with laboratory validation experiments and field observations, they become a powerful tool for investigating the dynamics of fault evolution. We present recent results from a new method that implements realistic grain evolution in 3D simulations of granular shear. The particle based model includes breakable bonds between individual particles allowing fracture of aggregate grains that are composed of many bonded particles. During simulations, particle motions and interactions as well as the mechanical behavior of the entire system are continuously monitored. We show that a model fault gouge initially characterized by mono-disperse spherical aggregate grains gradually evolves, with accumulated strain, to a wide size distribution composed of spherical and angular fragments. The comminution process yields a textural signature that is quantitatively comparable to natural and laboratory produced fault gouges. Mechanical behavior is comparable to a first order with relevant laboratory data. Simulations also reveal a strong correlation between regions of enhanced grain size reduction and localized strain. Thus in addition to producing realistic fault gouge textures, the model offers the possibility to explore direct links between strain partitioning and structural development in fault zones. This approach allows testing of fragmentation models and can reveal the sensitivity of different fragmentation processes to loading conditions, grain configurations and accumulated strain.
DE: 7209 Earthquake dynamics (1242)
DE: 8010 Fractures and faults
DE: 8030 Microstructures
DE: 8034 Rheology and friction of fault zones (8163)
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting