HR: 08:00h
AN: MR31B-01 INVITED     [Abstracts]
TI: Compaction, Permeability, and Deformation of Granular Rocks
AU: * Evans, B
EM: brievans@mit.edu
AF: Mass. Inst. Tech., Dept. EAPS, 54-718, Cambridge, MA 02139 United States
AB: The interplay among porosity, fluid flow, and deformation in granular materials gives rise to a rich variety of mechanical behavior. Recent field, laboratory, and theoretical investigations indicate that deformation modes in granular rocks, including compaction banding, dilation banding, or non-localized flow can be described using constitutive relations that involve double yield surfaces. Such yield-cap models have long been employed to describe deformation of soils, but these constitutive laws may actually apply to porous rocks under a very broad set of thermodynamic and loading conditions, including deformation at high pressure, at elevated temperatures, when mechanisms are strain rate dependent, and even when rocks are partially molten. Examples include unconsolidated granular minerals at low temperatures, porous mineral aggregates undergoing viscous creep at high temperatures, and partially molten granite and peridotite. Previous work by several groups indicates that the details of the yield envelope and the conditions necessary of localization in rocks deformed at lower temperatures depend on the triaxiality and geometry of the loading conditions and the geometry of the pore space. For viscously creeping rocks, recent experiments show that yield is also influenced by the volumetric and shear components of the strain rate. When viscous fluids are added to the pore space of granular rocks, fluid flow, permeability and the evolution of the pore space also are important parameters. Interestingly, under some circumstances experiments suggest that the relationship between volumetric strain rate and the rate of change of permeability is also affected by the details of the loading conditions.
DE: 1822 Geomechanics
DE: 3902 Creep and deformation
DE: 5104 Fracture and flow
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005