Basal force fluctuations and granular rheology: Linking macroscopic descriptions of granular flows to bed forces with implications for monitoring signals
arxiv(2023)
摘要
Granular flows are ubiquitous in nature with single flows traversing a wide
range of dynamic conditions from initiation to deposition. Many of these flows
are responsible for significant hazards and have the ability to generate
remotely detectable seismic signals. These signals provide a potential for
real-time flow measurements from a safe distance. To fully realize the benefit
of seismic measurements, basal granular forces must be linked to macroscopic
internal flow dynamics across a wide range of flow conditions. We utilize
discrete element simulations to observe dry and submerged granular flows under
plane-shear and inclined flow configurations, relating bulk kinematics to basal
force distributions. We find that force fluctuations scale with non-dimensional
shear-rate (I), and this scaling tracks three flow regimes that can be
described by μ(I) rheology, as well as a fourth regime that marks a `phase
change' from a liquid-like to a gas-like state: (1) an unsteady particle
rearrangement regime when I<10^-3, where basal forces are dominated by low
frequencies; (2) an intermediate regime when 10^-3< I<10^-2, where basal
forces start to become noise-like, (3) a transitional regime at
10^-210^-1, where the signal is nearly flat up
to a cutoff frequency. This effort suggests that basal forces can be used to
interpret complex granular processes in geophysical flows.
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