Discrete numerical simulation, quasistatic deformation and the origins of strain in granular materials

TL;DR

This paper uses systematic numerical simulations to identify two regimes of quasistatic deformation in dense granular materials, revealing different origins of strain and their implications for material behavior.

Contribution

It introduces a detailed numerical analysis distinguishing contact deformation and network instabilities as sources of strain in granular materials.

Findings

Two deformation regimes identified: contact deformation and network instabilities.

Strain from contact deformation can be modeled statically without inertia.

Material sensitivity increases near instability regimes.

Abstract

Systematic numerical simulations of model dense granular materials in monotonous, quasistatic deformation reveal the existence of two different r\'egimes. In the first one, the macroscopic strains stem from the deformation of contacts. The motion can be calculated by purely static means, without inertia, stress controlled or strain rate controlled simulations yield identical smooth rheological curves for a same sample. In the second r\'egime, strains are essentially due to instabilities of the contact network, the approach to the limits of large samples and of small strain rates is considerably slower and the material is more sensitive to perturbations. These results are discussed and related to experiments : measurements of elastic moduli with very small strain increments, and slow deformation (creep) under constant stress.