Particle velocity fields and depositional processes in laboratory ash flows, with implications for the sedimentation of dense pyroclastic flows

Girolami, Laurence; Roche, Olivier; Druitt, T. H.; Corpetti, Thomas

doi:10.1007/s00445-010-0356-9

Cited by 51 publications

(43 citation statements)

References 38 publications

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“…& The flow front of experimental flows shears over the substrate, but behind the flow front, a no slip relationship exists between the flow and the aggrading depositional surface (Girolami et al 2010). & In experimental flows with a grain size <60 μm, airparticle viscous interactions can cause a fluid to have inertial, water-like, flow behaviour .…”

Section: Implications For Flow Dynamics At the Time Of Deposition In mentioning

confidence: 99%

“…& After an initial phase of acceleration after release the flow fronts established a constant velocity that is a function of the initial height of release (square root of gh; Roche et al 2008). & Experimental granular flows deposit by progressive aggradation (Girolami et al 2010;Roche et al 2010).…”

Section: Implications For Flow Dynamics At the Time Of Deposition In mentioning

confidence: 99%

“…Relevance of experimental and modelling studies to understanding the flow behaviour of very large volume pyroclastic flows Many experimental studies and numerical simulations have been undertaken in recent years on the flow behaviour of high particle concentration granular flows (e.g. Roche et al 2005;Dufek and Bergantz 2007;Dellino et al 2007;Druitt et al 2007;Dufek and Manga 2008;Dufek et al 2009;Giordano and Dobran 1994;Girolami et al 2008Girolami et al , 2010Valentine and Wohletz 1989;Bursik and Woods 1996). The experiments all involve instantaneous lock release of small volumes of artificial beads or natural fine-ash mixtures from ignimbrite in small experimental tanks or down ramps.…”

Section: Implications For Flow Dynamics At the Time Of Deposition In mentioning

confidence: 99%

See 2 more Smart Citations

The flow dynamics of an extremely large volume pyroclastic flow, the 2.08-Ma Cerro Galán Ignimbrite, NW Argentina, and comparison with other flow types

et al. 2011

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Section: Implications For Flow Dynamics At the Time Of Deposition In mentioning

confidence: 99%

Section: Implications For Flow Dynamics At the Time Of Deposition In mentioning

confidence: 99%

Section: Implications For Flow Dynamics At the Time Of Deposition In mentioning

confidence: 99%

See 1 more Smart Citation

The flow dynamics of an extremely large volume pyroclastic flow, the 2.08-Ma Cerro Galán Ignimbrite, NW Argentina, and comparison with other flow types

et al. 2011

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“…This is correct at the fronts of air-fluidized flows, where the flow is plug-like, but not in their bodies, where pronounced velocity gradients and a static basal layer are observed (Girolami et al, 2010).…”

Section: Shallow Flow Descriptionmentioning

confidence: 80%

“…This feature is shared by other formulations of the vertical diffusion model (Iverson and Denlinger, 2001). Such a model induces a spatial distribution of the resistance to flow, which has been identified by many authors as a fundamental feature of water-or air-fluidized granular flows (Iverson, 2005;Ancey, 2007;Girolami et al, 2010) and appears to be of importance for the Jupille fly ash flow (lateral levees, steep flow front). Even nonfluidized granular flows display such a behavior, because of the dependence of the friction coefficient on the shear rate (Félix and Thomas, 2004;Mangeney et al, 2007).…”

Section: Pore Pressures Evolutionmentioning

confidence: 99%

Can the collapse of a fly ash heap develop into an air-fluidized flow? — Reanalysis of the Jupille accident (1961)

et al. 2015

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A fly ash heap collapse occurred in Jupille (Liege, Belgium) in 1961. The subsequent flow of fly ash reached a surprisingly long runout and had catastrophic consequences. Its unprecedented degree of fluidization attracted scientific attention. As drillings and direct observations revealed no water-saturated zone at the base of the deposits, scientists assumed an air-fluidization mechanism, which appeared consistent with the properties of the material. In this paper, the air-fluidization assumption is tested based on two-dimensional numerical simulations. The numerical model has been developed so as to focus on the most prominent processes governing the flow, with parameters constrained by their physical interpretation. Results are compared to accurate field observations and are presented for different stages in the model enhancement, so as to provide a base for a discussion of the relative influence of pore pressure dissipation and pore pressure generation. These results show that the apparently high diffusion coefficient that characterizes the dissipation of air pore pressures is in fact sufficiently low for an important degree of fluidization to be maintained during a flow of hundreds of meters.

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Autofluidization of pyroclastic flows propagating on rough substrates as shown by laboratory experiments

Chédeville

Roche

2014

JGR Solid Earth

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This study investigates the influence of the substrate surface roughness on the emplacement mechanisms of pyroclastic flows. We carried out laboratory experiments on gravitational flows generated from the release of initially fluidized or nonfluidized columns of fine particles (diameter d = 0.08 mm) in a horizontal channel. The roughness of the channel base was uniform in each experiment, created by gluing particles of diameter d 0 = 0.08 to 6 mm to the base. Other things being equal, the flow runout distance increased with the channel base roughness (d 0 ) to a maximum of about twice that of flows on a smooth substrate when d 0 = 1.5-3 mm, before decreasing moderately at higher roughness values of d 0 = 6 mm. Long runout originated mainly during the late stages of emplacement as flow deceleration was strongly reduced at high substrate roughness. This was caused by (partial) autofluidization due to an upward air flux escaping from the substrate interstices in which flow particles settled. Autofluidization was evidenced by high pore fluid pressure measurements at the base of initially nonfluidized flows and also by reduced flow runout when the interstices were initially partially filled so that less air was available. Furthermore, the runout distance of flows of large particles (d = 0.35 mm), which could not be fluidized by the ascending air flux, was independent of the substrate roughness. This study suggests that autofluidization caused by air escape from the interstices of a rough substrate is one important mechanism to explain the common long runout distance of pyroclastic flows even on subhorizontal topographies.

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Particle velocity fields and depositional processes in laboratory ash flows, with implications for the sedimentation of dense pyroclastic flows

Abstract: International audienc

Cited by 51 publications

References 38 publications

The flow dynamics of an extremely large volume pyroclastic flow, the 2.08-Ma Cerro Galán Ignimbrite, NW Argentina, and comparison with other flow types

The flow dynamics of an extremely large volume pyroclastic flow, the 2.08-Ma Cerro Galán Ignimbrite, NW Argentina, and comparison with other flow types

Can the collapse of a fly ash heap develop into an air-fluidized flow? — Reanalysis of the Jupille accident (1961)

Autofluidization of pyroclastic flows propagating on rough substrates as shown by laboratory experiments

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