Deformation and Frictional Failure of Granular Media in 3D Analog and Numerical Experiments

• Published in: Pure and applied geophysics Vol. 181; no. 7; pp. 2083 - 2105
• Main Authors: Ioannidi, P. I., McLafferty, S., Reber, J. E., Morra, G., Weatherley, D.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01-07-2024; Springer Nature B.V
• Subjects: Comminution; Deformation; Discrete element method; Earth and Environmental Science; Earth Sciences; Elastoplasticity; Experiments; Geophysics/Geodesy; Grain boundaries; Granular materials; Granular media; Internal friction; Laboratory experimentation; Laboratory experiments; Mathematical models; Numerical experiments; Numerical models; Shear stress; Shear zone; Sliding; Slip; Slumping; grain comminution; analog experiments; Granular media; discrete element method; frictional failure
• DOI: 10.1007/s00024-024-03464-6
• EISSN: 1420-9136
• ISSN: 0033-4553

Frictional sliding along grain boundaries in brittle shear zones can result in the fragmentation of individual grains, which ultimately can impact slip dynamics. During deformation at small scales, stick–slip motion can occur between grains when existing force chains break due to grain rearrangement or failure, resulting in frictional sliding of granular material. The rearrangement of the grains leads to dilation of the granular package, reducing the shear stress and subsequently leading to slip. Here, we conduct physical experiments employing HydroOrbs, an elasto-plastic material, to investigate grain comminution in granular media under simple shear conditions. Our findings demonstrate that the degree of grain comminution is dependent on both the normal force and the size of the grains. Using the experimental setup, we benchmark Discrete Element Method (DEM) numerical models, which are capable of simulating the movement, rotation, and fracturing of elasto-plastic grains subjected to simple shear. The DEM models successfully replicate both grain comminution patterns and horizontal force fluctuations observed in our physical experiments. They show that increasing normal forces correlate with higher horizontal forces and more fractured grains. The ability of our DEM models to accurately reproduce experimental results opens up new avenues for investigating various parameter spaces that may not be accessible through traditional laboratory experiments, for example, in assessing how internal friction or cohesion affect deformation in granular systems.