A discrete element model for the development of compaction localization in granular rock

Abstract

A discrete element model was developed to simulate the micromechanics of compaction localization in a granular rock. The rock was modeled as a bonded assembly of circular disks, and seven different distributions of radius were considered. To simulate grain crushing and pore collapse, an intragranular damage mechanism was introduced that allows for the shrinkage of a disk if one of its normal contact stresses attains a critical value. The model captures key attributes of failure mode and damage evolution associated with the brittle-ductile transition in porous sandstones. Our simulations indicate that the development of discrete compaction bands is promoted in a relatively homogeneous granular aggregate, while diffuse band growth and distributed cataclastic flow are preferred modes of compaction in a more heterogeneous system. To interpret the former result an Eshelby inclusion model was proposed to estimate analytically the local stress perturbations due to pore collapse in a homogeneous aggregate. Copyright 2008 by the American Geophysical Union.