Journal
INTERNATIONAL JOURNAL OF SEDIMENT RESEARCH
Volume 35, Issue 4, Pages 315-327Publisher
IRTCES
DOI: 10.1016/j.ijsrc.2020.03.001
Keywords
Debris flow; Rheology; Grain concentration; Herschel-Bulkley model
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The rheological behavior of natural slurries consisting of fine-grained, reconstituted debris-flow deposits on pyroclastic terrains having different solid concentrations (ranging from 30 to 42%) has been investigated using a rotational rheometer equipped with a vane rotor system. Experiments were done by increasing the applied shear stress step by step; then a decreasing stress ramp was applied following the same shear stress levels. The slurry mixtures exhibit a typical yield-stress fluid behavior with a static yield stress larger than the dynamic yield stress. In the range of the shear rate corresponding to the flowlike behavior the slurry mixtures behave as a dilatant fluid at lower grain concentrations and as a pseudoplastic fluid in correspondence with the higher grain content, showing a strong discrepancy from the Bingham idealization. The rheological behavior is better interpreted by a Herschel-Bulkley model, whose rheological parameters strongly depend on the granular concentration. Therefore, a generalized Herschel-Bulkley model accounting for the bulk sediment concentration effect is proposed. (C) 2020 International Research and Training Centre on Erosion and Sedimentation/the World Association for Sedimentation and Erosion Research. Published by Elsevier B.V. All rights reserved.
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