The perfect debris flow? Aggregated results from 28 large-scale experiments

Aggregation of data collected in 28 controlled experiments reveals reproducible debris‐flow behavior that provides a clear target for model tests. In each experiment ∼10 m3 of unsorted, water‐saturated sediment composed mostly of sand and gravel discharged from behind a gate, descended a steep, 95‐m...

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Veröffentlicht in:	Journal of Geophysical Research. F. Earth Surface Jg. 115; H. F3
Hauptverfasser:	Iverson, Richard M., Logan, Matthew, LaHusen, Richard G., Berti, Matteo
Format:	Journal Article
Sprache:	Englisch
Veröffentlicht:	Washington, DC Blackwell Publishing Ltd 01.09.2010 American Geophysical Union
Schlagworte:	Boundary conditions Debris Debris flow Detritus Dispersions Earth sciences Earth, ocean, space Exact sciences and technology experiments Flow resistance Fractals Geomorphology Geophysics Gravel Hydrology Landslides & mudslides Levees Mathematics Mud Nonlinear systems Particle size pore pressure Porosity Rheology Roughness Sediments Segregations Time series experimental studies models mobility thickness pore fluid debris flows aggregation friction grains gravel sand grain size Normal stress fluid pressure pore pressure roughness debris Flow velocity Height flumes segregation mud boundary conditions flow
ISSN:	0148-0227, 2169-9003, 2156-2202, 2169-9011
Online-Zugang:	Volltext
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Zusammenfassung:	Aggregation of data collected in 28 controlled experiments reveals reproducible debris‐flow behavior that provides a clear target for model tests. In each experiment ∼10 m3 of unsorted, water‐saturated sediment composed mostly of sand and gravel discharged from behind a gate, descended a steep, 95‐m flume, and formed a deposit on a nearly horizontal runout surface. Experiment subsets were distinguished by differing basal boundary conditions (1 versus 16 mm roughness heights) and sediment mud contents (1 versus 7 percent dry weight). Sensor measurements of evolving flow thicknesses, basal normal stresses, and basal pore fluid pressures demonstrate that debris flows in all subsets developed dilated, coarse‐grained, high‐friction snouts, followed by bodies of nearly liquefied, finer‐grained debris. Mud enhanced flow mobility by maintaining high pore pressures in flow bodies, and bed roughness reduced flow speeds but not distances of flow runout. Roughness had these effects because it promoted debris agitation and grain‐size segregation, and thereby aided growth of lateral levees that channelized flow. Grain‐size segregation also contributed to development of ubiquitous roll waves, which had diverse amplitudes exhibiting fractal number‐size distributions. Despite the influence of these waves and other sources of dispersion, the aggregated data have well‐defined patterns that help constrain individual terms in a depth‐averaged debris‐flow model. The patterns imply that local flow resistance evolved together with global flow dynamics, contradicting the hypothesis that any consistent rheology applied. We infer that new evolution equations, not new rheologies, are needed to explain how characteristic debris‐flow behavior emerges from the interactions of debris constituents.
Bibliographie:	istex:0D3F46950F12A2173108FBCE812698E5147499D9 ArticleID:2009JF001514 ark:/67375/WNG-LJLRGHVV-0 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 14 ObjectType-Article-1 ObjectType-Feature-2 content type line 23
ISSN:	0148-0227 2169-9003 2156-2202 2169-9011
DOI:	10.1029/2009JF001514