The nature of quasistatic deformation in granular materials
Strain in granular materials in quasistatic conditions under varying stress originate in (I) contact deformation and (II) rearrangements of the contact network. Depending on sample history and applied load, eiter mechanism might dominate. One may thus define rheological regimes I and II accordingly. Their porperties are presented and illustrated here with discrete numerical simulatiion results in 2 and 3 dimensions. This discussion of the microscopic physical origin of strain is shown to clarify such issues as the existence of macroscopic elasticity, the approach to stress-strain relations in the large system limit and the sensitivity to noise.