期刊
CANADIAN GEOTECHNICAL JOURNAL
卷 54, 期 2, 页码 258-269出版社
CANADIAN SCIENCE PUBLISHING
DOI: 10.1139/cgj-2015-0532
关键词
debris flow; dimensionless number; flow regime; plane laser-induced fluorescence; flume model tests
资金
- Marsden Fund of the Royal Society of New Zealand at the University of Canterbury, New Zealand, under the grant The Internal Mechanics of Debris Flows
- Engineering and Physical Sciences Research Council (EPSRC), UK, under High speed granular debris flows: new paradigms and interactions in geomechanics [EP/M017427/1]
- EPSRC [EP/M017427/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/M017427/1] Funding Source: researchfish
Physical modelling of debris flow in a small-scale flume has been carried out to investigate the internal stress-transfer mechanisms within unsteady, saturated, and segregating granular free-surface flows. Measurements of the internal velocity fields within model flows were obtained via planar laser-induced fluorescence and particle image velocimetry. Normalized velocity profiles taken at a section over the flow duration were found to essentially collapse onto a single curve, the shape of which was dependent on the particle-size distribution. While all flows exhibited internal basal slip and shear, for tests on well-graded materials that are most representative of debris flows, the shear rate was found to reduce towards the surface to near-zero, exhibiting near plug-flow. Dimensional analysis shows that particles of different size within these flows experienced different dominant stress-transfer mechanisms-frictional, collisional or viscous. Rapid grain-size segregation therefore is both due to and results in different modes of stress transfer within a single flow. This means that in a segregating and hence, stratified system, different flow regimes will act concurrently at microscale and mesoscale. Results highlight the complexity of debris flows, so that it may be undesirable to ascribe a single microscale constitutive behaviour throughout, and further calls into question the concept of flow regimes for debris flows based on bulk measurements.
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