Accelerating failure in numerical models of shearing granular layers
Abstract
Two-dimensional numerical simulations of shear in a gravity-free layer of circular grains were conducted to illuminate the basic mechanics of shear of granular layers (such as layers of fault gouge). Under a certain range of boundary conditions our simulated granular layers exhibit stick-slip motion. This stick-slip behavior is characterized by prolonged intervals when the granular layer is "stuck", followed by failure and rapid shearing motion of the whole layer. Our results show that the micromechanics of contact forces between grains is responsible for stick-slip behavior and for changes in effective strength of the layer: During the "stuck" phase, and in preparation for slip, more and more of grain-contacts which carry low forces start sliding, resulting in accelerating Benioff strain. When enough of the low-force contacts frictionally slide, the granular layer weakens and losses some rigidity, leading to motion of contacts that carry larger forces and to large-scale slip. Our results have implications to understanding failure in granular layers and in faults in general.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....8371A