Granular suspension avalanches. II. Plastic regime

Andreini, Nicolas; Ancey, Christophe; Épely-Chauvin, Gaël

doi:10.1063/1.4793720

Cited by 9 publications

(18 citation statements)

References 59 publications

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“…The depth at which this transition occurred was systematically larger than the critical depth found by Bonnoit et al, 39 but their respective values were close to each other: it occurred for h between 2 and 3 cm, with ξ ranging from 0.6 to 1.2 cm when the solids fraction was increased from 0.575 to 0.595. Importantly, we observed the transition to more complicated flow regimes (the fracture and plastic regimes), which was not observed by others (see Paper II 46 ).…”

Section: Discussionsupporting

confidence: 55%

“…We referred to this regime as the macro-viscous regime. At longer times, the free surface became more and more bumpy as the bulk fractured (see Paper II 46 ). Eventually, the granular suspension moved intermittently: episodes of slipping were followed by short periods of rest.…”

Section: Discussionmentioning

confidence: 99%

“…(A9), the front was blunter than the theory predicted. As explained in Paper II, 46 the development of waves on a free surface was the consequence of fractures that grew in size in the course of motion, but the exact mechanism remains unknown.…”

Section: Further Analysis: Run Imentioning

confidence: 99%

“…We observed that for the sieved suspensions at the highest concentrations (Runs B, C, and D), the experimental curves diverged from the similarity solution at long times and this departure was even more marked when increasing the particle concentration to 58% or 59%. For Run D, the flow seemed to come to a halt, but in fact it entered a stick-slip regime, in which the front moved forward intermittently (see Paper II 46 about the plastic regime). For the unsieved suspensions, the experimental curves lie slightly above the similarity solution, which may be an indication of particle migration.…”

Section: B Macro-viscous Regime: Outlinementioning

confidence: 99%

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Granular suspension avalanches. I. Macro-viscous behavior

2013

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We experimentally studied the flow behavior of a fixed volume of granular suspension, initially contained in a reservoir and released down an inclined flume. Here "granular suspension" refers to a suspension of non-Brownian particles in a viscous fluid. Depending on the solids fraction, density mismatch, and particle size distribution, a wealth of behaviors can be observed. Here we report and interpret results obtained with granular suspensions, which consisted of neutrally buoyant particles with a solids fraction (φ = 0.575-0.595) close to the maximum random packing fraction (estimated at φ m = 0.625). The particles had the same refractive index as the fluid, which made it possible to measure the velocity profiles inside the moving bulk and far from the sidewalls. Additional information such as the front position and the flow depth was also recorded. Three regimes were observed. At early times, the flow features were reminiscent of homogeneous Newtonian fluids (e.g., the same dependence of the front position on time). At later times, the free surface became more and more bumpy as fractures developed within the bulk. This fracture process ultimately gave rise to a stick-slip regime, in which the suspension moved intermittently. In this paper, we focus on the first regime referred to as the macroviscous regime. Although the bulk flow properties looked like those of Newtonian fluids, the internal dynamics were much richer. C 2013 American Institute of Physics.

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Section: Discussionsupporting

confidence: 55%

Section: Discussionmentioning

confidence: 99%

Section: Further Analysis: Run Imentioning

confidence: 99%

Section: B Macro-viscous Regime: Outlinementioning

confidence: 99%

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Granular suspension avalanches. I. Macro-viscous behavior

2013

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“…On the other hand, a loosely packed assembly contracts in response to shearing. These processes play a dramatic role in the dynamics of fluidized granular flows, from their initial destabilization to their final deposition (Andreini et al 2013;Iverson et al 2010;George and Iverson 2011;Montserrat et al 2012;Rondon et al 2011;Iverson and George 2016).…”

Section: Introductionmentioning

confidence: 99%

A two-phase two-layer model for fluidized granular flows with dilatancy effects

et al. 2016

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We propose a two-phase two-thin-layer model for fluidized debris flows that takes into account dilatancy effects, based on the closure relation proposed by Roux and Radjai (1998). This relation implies that the occurrence of dilation or contraction of the granular material depends on whether the solid volume fraction is respectively higher or lower than a critical value. When dilation occurs, the fluid is sucked into the granular material, the pore pressure decreases and the friction force on the granular phase increases. On the contrary, in the case of contraction, the fluid is expelled from the mixture, the pore pressure increases and the friction force diminishes. To account for this transfer of fluid into and out of the mixture, a two-layer model is proposed with a fluid layer on top of the two-phase mixture layer. Mass and momentum conservation are satisfied for the two phases, and mass and momentum are transferred between the two layers. A thin-layer approximation is used to derive average equations, with accurate asymptotic expansions. Special attention is paid to the drag friction terms that are responsible for the transfer of momentum between the two phases and for the appearance of an excess pore pressure with respect to the hydrostatic pressure. For an appropriate form of dilatancy law we obtain a depth-averaged model with a dissipative energy balance in accordance with the corresponding 3D initial system.

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Dynamics of glide avalanches and snow gliding

Ancey

Bain²

2015

Reviews of Geophysics

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In recent years, due to warmer snow cover, there has been a significant increase in the number of cases of damage caused by gliding snowpacks and glide avalanches. On most occasions, these have been full-depth, wet-snow avalanches, and this led some people to express their surprise: how could low-speed masses of wet snow exert sufficiently high levels of pressure to severely damage engineered structures designed to carry heavy loads? This paper reviews the current state of knowledge about the formation of glide avalanches and the forces exerted on simple structures by a gliding mass of snow. One particular difficulty in reviewing the existing literature on gliding snow and on force calculations is that much of the theoretical and phenomenological analyses were presented in technical reports that date back to the earliest developments of avalanche science in the 1930s. Returning to these primary sources and attempting to put them into a contemporary perspective are vital. A detailed, modern analysis of them shows that the order of magnitude of the forces exerted by gliding snow can indeed be estimated correctly. The precise physical mechanisms remain elusive, however. We comment on the existing approaches in light of the most recent findings about related topics, including the physics of granular and plastic flows, and from field surveys of snow and avalanches (as well as glaciers and debris flows). Methods of calculating the forces exerted by glide avalanches are compared quantitatively on the basis of two case studies. This paper shows that if snow depth and density are known, then certain approaches can indeed predict the forces exerted on simple obstacles in the event of glide avalanches or gliding snow cover.

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Granular suspension avalanches. II. Plastic regime

Cited by 9 publications

References 59 publications

Granular suspension avalanches. I. Macro-viscous behavior

Granular suspension avalanches. I. Macro-viscous behavior

A two-phase two-layer model for fluidized granular flows with dilatancy effects

Dynamics of glide avalanches and snow gliding

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