Efficacy of simple continuum models for diverse granular intrusions

Granular intrusion is commonly observed in natural and man-made settings. Unlike single-phase media like solids and fluids, granular media can simultaneously display fluid-like and solid-like characteristics in a variety of intrusion scenarios. This trans-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 multiphase behavior by modeling the media at the grain scale, but interest often lies in the macro-scale characterizations of such systems. We examine the efficacy of a macro-scale continuum approach in modeling and understanding the physics and macroscopic phenomena behind a variety of granular intrusions cases using two basic frictional yielding constitutive models. We compare predicted granular force response and material flow to data in four 2D intrusion cases: (1) depth-dependence forces responses 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 in vertical plate intrusions in under-compacted granular media. Our continuum modeling approach captures the flow process and drag forces in each of these cases compared to experimental data while providing key meso- and macro-scopic insights. Our study highlights how continuum modeling approaches provide an alternative for efficient modeling as well as conceptual understanding of various granular intrusion phenomena