  Granular intrusion is commonly observed in natural and human-made settings.
Unlike typical solids and fluids, granular media can simultaneously display
fluid-like and solid-like characteristics in a variety of intrusion scenarios.
This multi-phase behavior increases the difficulty of accurately modeling these
and other yielding (or flowable) materials. Micro-scale modeling methods, such
as DEM (Discrete Element Method), capture this behavior by modeling the media
at the grain scale, but there is often interest in the macro-scale
characterizations of such systems. We examine the efficacy of a macro-scale
continuum approach in modeling and understanding the physics of various
macroscopic phenomena in a variety of granular intrusion cases using two basic
frictional yielding constitutive models. We compare predicted granular force
response and material flow to experimental data in four quasi-2D intrusion
cases: (1) depth-dependent force response in horizontal submerged-intruder
motion; (2) separation dependent drag variation in parallel-plate
vertical-intrusion; (3) initial-density-dependent drag fluctuations in free
surface plowing, and (4) flow zone development during vertical plate intrusions
in under-compacted granular media. Our continuum modeling approach captures the
flow process and drag forces while providing key meso- and macro-scopic
insights. The modeling results are then compared to experimental data. Our
study highlights how continuum modeling approaches provide an alternative for
efficient modeling as well as a conceptual understanding of various granular
intrusion phenomena.
