Journal
INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES
Volume 45, Issue 10, Pages 2785-2798Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijsolstr.2007.11.028
Keywords
rocks; grain-boundary sliding; inelastic dilatancy; brittle-ductile transition
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This work introduces a micro-mechanical grain-aggregate model and numerical simulation capability to study the combined effects of grain-boundary slip and separation, as well as grain-interior plasticity on the overall deformation of compact rocks. Two major conclusions can be drawn from our simulation study: (i) At sufficiently low confining pressures, the widely-observed inelastic dilatant response in compact rocks under compression is attributable to the geometrically-mismatched grain-boundary sliding and concomitant formation of triple-junction cracks which result in an increase in volume. Failure patterns change from splitting-fracture at low confining pressures, to distributed micro-cracking in macroscopic shear-bands as the confining pressure increases. (ii) When the confining pressure increases to an amount such that grain-boundary sliding is suppressed due to frictional effects, the inelastic dilatancy effects disappear, and isochoric grain-interior plasticity takes over to accommodate the imposed external deformation, and this is the major cause of the brittle-ductile transition in these materials. (c) 2008 Elsevier Ltd. All rights reserved.
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