The role of plastic deformation in compaction of granular matter at high pressures

While granular matter can often be effectively rigid, this is not always the case in many industrial or geophysical applications where particles can be quite soft relative to applied forces. Under such pressures, an important densification mechanism in many materials is plastic deformation. To simulate this process, we use a bonded particle model which represents each grain as a collection of computational nodes connected by elastic-plastic springs that plastically activate at a strain $\epsilon_p$ to explicitly model intragranular mechanics using LAMMPS. By isotropically compacting 1,024 spherical grains, we quantify changes in curves of pressure vs. packing fraction due to plasticity compared to the fully elastic limit. All systems initially track the fully elastic response as they compact up to a $\epsilon-p$-dependent packing fraction above which there is a reduction in the relative pressure. By scaling data using a power of $\epsilon-p$, we find these curves can be collapsed. These findings are related to both the macroscopic properties of the bulk granular material and the microscopic statistics of individual bonds in the system.



Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525.