Breaking size-segregation waves and mobility feedback in dense granular avalanches

Vaart, Kasper van der; Thornton, Anthony Richard; Johnson, Chris; Weinhart, Thomas; Jing, Lü; Gajjar, Parmesh; Gray, J.O.; Ancey, Christophe

doi:10.1007/s10035-018-0818-x

Cited by 17 publications

(33 citation statements)

References 79 publications

(171 reference statements)

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“…Therefore, we see that the inflow velocity is decreasing with time, in the discrete particle simulations, and lower than the steady-flow relation, (3.28), used by the continuum model. This is similar to the complex feedback between segregation profile, friction and hence velocity, seen in the breaking size-segregation structures studied by [88] and is not captured by the current continuum models.…”

Section: Height Profilessupporting

confidence: 57%

“…The exact relation between the macroscopic friction coefficients and flow-height for a bidisperse granular flow within the bulbous head needs further investigation. However, a detailed investigation of this relationship, for the similar constant height breaking wave-structure can be found in van der Vaart et al [88] The shock speed of u f ≈ 1.9 is significantly lower than the outflow speed,ū out ≈ 3.1, which might look surprising at first. However, we assume that the velocity of the flow at the surface is higher than at the base, varying linearly as described by (3.4).…”

Section: Ode Solutionmentioning

confidence: 53%

“…Behind that, there is an expanding structure around the shock position, see figure 3.8. The structure observed here in the discrete particle simulations has been predicted from a non-depth-averaged continuum model [41,89,90] and in both experiments and discrete particle simulations of a moving belt [88]. This structure was named the breaking size-segregation wave and its study is ongoing.…”

Section: Segregation Profilesmentioning

confidence: 56%

“…The discrete particle simulations display smoother behaviour than the continuum model, where the mass of the particles is also slightly more in the back compared to the numerical solution of the continuum model. We suspect the disagreement in the continuum and discrete particle simulations stems from the fact that the segregationstructure in the front is approximated by a shock rather than the full structure of the breaking-size-segregation wave, that is expected at the back of the bulbous head [88][89][90]. This difference modified the effective basal friction; and, hence, the bulk dynamics and shape of the front.…”

Section: Height Profilesmentioning

confidence: 98%

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On segregation in bidisperse granular flows

Denissen¹

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We consider a monodisperse dry granular material flowing down a rough inclined channel with downslope contracting sidewalls: theoretically and numerically. Utilising the depth-averaged shallow granular theory together with an empirical, but discrete particle simulations validated constitutive friction law, an extended novel one-dimensional (depth-and width-averaged) granular hydraulic theory is presented. For steady flows, besides describing the subcritical flow state, the one-dimensional model also predicts two other steady states, for a range of upstream prescribed flow conditions and channel openings. These states are supercritical flows with weak oblique shocks (smooth when widthaveraged) and flows with a steady jump in the contraction region. Both, super-and subcritical flow states were verified by numerically solving the depth-averaged two-dimensional shallow granular model. Despite the strong inhomogeneities in the linear contraction region, the one-and two-dimensional solutions (averaged across the channel) incomparably match well.

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Section: Height Profilessupporting

confidence: 57%

Section: Ode Solutionmentioning

confidence: 53%

Section: Segregation Profilesmentioning

confidence: 56%

Section: Height Profilesmentioning

confidence: 98%

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On segregation in bidisperse granular flows

Denissen¹

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“…e movement and accumulation processes of graded grains are complicated. At present, the understanding of the mechanism of grain-size segregation is not deep enough, so it still needs constant study [48,49]. e grain size distribution determines the partitioning of the physicomechanical properties of the deposits in front of the RNB including the density, porosity, and permeability, which is the premise for the study of the forces on the RNB and for the stability analysis and cleanup of deposits.…”

Section: Influence Of Grain Size Gradationmentioning

confidence: 99%

Research on the Obstruction Process of Rigid Netting Barriers toward Granular Flow

Fan

2019

Advances in Civil Engineering

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With the advantages of a simple structure and rapid construction, the rigid netting barrier (RNB) exerts a good obstruction effect on granular flow and is a common engineering measure used to prevent geological disasters in the form of granular flows. However, due to the limitations of current measuring and testing techniques, it is difficult to obtain an accurate measurement of the granular flow velocity and the impact force of granular flow on the mesh structures that are of primary concern in the design of protective structures. To study the characteristics of the obstruction process of RNBs toward granular flow, a typical impact experiment involving granular flow was numerically simulated by the discrete element method, and the correctness and effectiveness of the calculation method were also verified. On this basis, the discrete element method was applied to simulate the obstruction process affecting granular flow under different RNB setting conditions, and the calculation results clearly present the phenomena that occur during the obstruction process of RNBs toward granular flow, such as “run-up,” “overflow,” “passing-through,” and “grain-size segregation.” By analyzing the effects of these phenomena on the obstruction efficiency and the time history of the forces acting on the RNB, the rational setting of an RNB was further discussed. This study can provide a reference for the engineering application of RNB.

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Flume Modeling of Debris Flows

Choi,

Ng,

Liu

2024

Geoenvironmental Disaster Reduction

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Debris flows are complex mixtures of water and soil, which range from clay to boulder size, that surge downslope under the influence of gravity. Debris flows are unique compared to other types of landslides (e.g., rock avalanches; dry granular flows) because their dynamics are governed by both the soil grains and interstitial fluid. On one hand, debris flows may exhibit some features of dry granular flows, such as particle size segregation. On the other hand, contact and collisional grain stresses are strongly influenced by the viscosity and excess pressure of the interstitial fluid. Furthermore, debris flows travel over complex erodible boundaries and have been reported to reach volumes of up to 10 9 m 3 and travel kilometers in length. Evidently, the scale and dynamics of natural debris flows are complex and difficult to reproduce. One of the most common approaches to investigate the dynamics of debris flows is by conducting experiments, which provide idealized and high-quality evidence to evaluate theoretical and numerical models. This chapter provides an overview of the fundamental principles, scaling considerations, commonly adopted setups (e.g., flumes and geotechnical centrifuge), and the state-of-the-art in instrumentation and image analysis for modeling debris flows.

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Breaking size-segregation waves and mobility feedback in dense granular avalanches

Cited by 17 publications

References 79 publications

On segregation in bidisperse granular flows

On segregation in bidisperse granular flows

Research on the Obstruction Process of Rigid Netting Barriers toward Granular Flow

Flume Modeling of Debris Flows

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