Abstract
AbstractGranular materials are central to a wide range of geologic concerns, but until now there has been no experimental or theoretical exploration of the relative influence of material characteristics typical of geological flows on overall rheology. Shearing samples from 50–300 rad/s under constant pressure 3.5 kPa, we measure dilation and fluctuation energy and establish what combination of parameters best predicts flow behavior. In fast granular flows, dilation results from fluctuation energy, but their precise relationship depends on dissipative processes. The best predictor of dissipation is characteristic length of plastic displacement, δ. Flows that have greater plastic deformation within grains (higher δ) dilate more for a given increase in fluctuation energy. This counterintuitive result likely stems from the reduced efficiency of energy transfer to more distant parts of the shear flow. The fact that mineralogy's effect on high‐velocity granular flows is captured by the material's propensity to absorb energy through plastic damage or release energy through fracture is useful for understanding energy partitioning in granular flows and predicting the shear behavior of a wide range of geological materials.
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