Dilatancy in dry granular flows with a compressible μ(I) rheology

Bouchut, François; Fernández-Nieto, Enrique D.; Koné, El Hadji; Mangeney, A.; Narbona-Reina, Gladys

doi:10.1016/j.jcp.2020.110013

Cited by 12 publications

(5 citation statements)

References 39 publications

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“…The experimental data show that the passage of the flow front at a given point is followed by a short under-pressure phase and a later and longer over-pressure phase. Roche et al (2010) propose that the under-pressure stage is mainly caused by the basal slip boundary condition and possibly by dilatancy processes (Garres-Díaz et al 2020;Bouchut et al 2021), which is supported by simulations (Breard et al 2019a). Moreover, the minimum value reached during the under-pressure phase was empirically correlated to the slip velocity (𝑢 slip ; Roche 2012).…”

Section: Simulations On Horizontal Planesmentioning

confidence: 61%

“…We show that the relationship between distance along the channel and the maximum pressure reached during the flow passage is remarkably similar in simulations and experiments, which indicates that our model is able to capture reasonably well the evolution of pore pressure within the granular flow. This suggests that the effect of compaction and dilatancy processes (Bouchut et al 2016(Bouchut et al , 2021 is limited once the flow front has passed, and that the pore pressure effect in the propagation of granular flows can be modeled considering only advection. Moreover, we show that the magnitude of the under-pressure phase measured in experiments can be successfully quantified by considering the slip velocity at the channel base, as proposed by Breard et al (2019a).…”

Section: Discussionmentioning

confidence: 99%

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The influence of gas pore pressure in dense granular flows: numerical simulations versus experiments and implications for pyroclastic density currents

et al. 2021

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We investigate the influence of gas pore pressure in granular flows through numerical simulations on horizontal and low-angle inclined surfaces. We present a two-phase formulation that allows description of dam-break experiments considering high-aspect-ratio collapsing columns and depth-dependent variations of flow properties. The model is confirmed by comparing its results with data of analogue experiments. The results suggest that a constant, effective pore pressure diffusion coefficient can be determined in order to reproduce reasonably well the dynamics of the studied dam-break experiments, with values of the diffusion coefficient consistent with experimental estimates from defluidizing static columns. The discrepancies between simulations performed using different effective pore pressure diffusion coefficients are mainly observed during the early acceleration stage, while the final deceleration rate, once pore pressure has been dissipated, is similar in all the studied numerical experiments.However, these short-lasting discrepancies in the acceleration stage can be manifested in large differences in the resulting run-out distance. We also analyze the pore pressure at different distances along the channel. Although our model is not able to simulate the under-pressure phase generated by the sliding head of the flows in experiments and measured beneath the flowsubstrate interface, the spatio-temporal characteristics of the subsequent over-pressure phase are compatible with experimental data. Additionally, we studied the deposition dynamics of the granular material, showing that the timescale of deposition is much smaller than that of the granular flow, while the time of the deposition onset varies as a function of the distance from the reservoir, being strongly controlled by the surface slope angle. The simulations reveal that an increment of the surface slope angle from 0° to 10° is able to increase significantly the flow run-out distance (by a factor between 2.05 and 2.25, depending on the fluidization conditions). This has major implications for pyroclastic density currents, which typically propagate at such gentle slope angles.

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Section: Simulations On Horizontal Planesmentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

The influence of gas pore pressure in dense granular flows: numerical simulations versus experiments and implications for pyroclastic density currents

et al. 2021

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“…On the other hand, it is worth highlighting that our model considers a constant pore pressure diffusion coefficient, which may not reflect correctly the behavior of fluidized flows in nature due to a series of factors such as dilatancy and compaction [30,31], which should be considered in future studies to deepen our understanding about the relationship between pore pressure diffusion in granular flows and their dimensions.…”

Section: Relationship Between Pore Pressure Diffusion Coefficient And...mentioning

confidence: 99%

“…Fluidization is the result of the differential motion between solid particles and interstitial gas, whose interplay is able to generate pore pressure, counterbalance partially or entirely the solid particle weight, and thus reduce particle friction [17,[19][20][21][22][23][24]. In the context of PDCs, fluidization is mainly generated at the impact zone of a collapsing fountain [25][26][27][28], while the temporal evolution of fluidization is the result of the coupled effect of diffusion, advection, dilatancy, compaction and air entrainment [29][30][31], which are strongly influenced by the grain-size distribution of the solid particles [18,32] and the underlying topography [11,33].…”

Section: Introductionmentioning

confidence: 99%

Effect of fluidization in increasing the run-out distance of granular flows generated from different aspect ratio collapsing columns

Aravena,

Chupin,

Dubois

et al. 2024

Preprint

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We investigate the propagation dynamics of fluidized granular flows in a horizontal channel in order to evaluate the factors controlling the efficiency of fluidization in increasing the run-out distance of natural granular mixtures such as pyroclastic density currents. For this, we use a two-phase numerical model able to simulate dam-break experiments, which permits us to describe depth-dependent variations of flow properties and the effect of pore pressure on the rheology of the granular material. We show that the interplay between column collapse timescale and flow front velocity plays a primary role in determining the effective influence of fluidization on run-out distance. For high aspect ratio columns, collapse velocity decreases abruptly after reaching its peak, a significant portion of the collapse occurs when the flow front has travelled a long distance from the reservoir and, importantly, the decrease of basal pore pressure with time in the reservoir translates into a reduced velocity of the granular material entering into the propagation channel during final phases of collapse. Thus, at some point, the collapsing material is not able to affect significantly the flow front dynamics, in contrast to low aspect ratio collapsing columns. These results are consistent with complementary analogue experiments, which show that the granular material at the front of the deposit originates from lower levels of the collapsed column. Comparison with new experimental data also reveals that the effective pore pressure diffusion coefficient is an increasing function of column height, and can be considered as proportional to a weighted average of flow thickness during propagation. This is consistent with experiments on static defluidization columns, but had not been tested in dam-break experiments until this study. Considering this type of dependency, under our experimental and simulation conditions, the non-dimensional run-out distance presents a relative maximum for an aspect ratio between \(1\) and \(2\), and then it decreases abruptly. Our observations suggest that the effect of fluidization in increasing run-out distance is limited under conditions of sudden collapse of a volume of fluidized material with no initial velocity, such as collapsing domes. This has implications for the long-lasting debate on the influence of fluidization in the transport dynamics of natural granular flows.

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“…Roux & Radjai 1997;Rondon et al 2011;Pailha & Pouliquen 2009;Bouchut et al 2016aBouchut et al ,b, 2021. This compressibility impacts the shape and velocity of the flow and thus may be a source of error when not accounted for in numerical models, especially for granular flows under water (Rondon et al 2011;Bouchut et al 2021;Rauter 2021). We quantify these effects here to better interpret the comparison between incompressible codes and experimental results and therefore discriminate the origins of the error.…”

Section: Dilatation Of the Granular Materialsmentioning

confidence: 99%

Performance and limits of a shallow-water model for landslide-generated tsunamis: from laboratory experiments to simulations of flank collapses at Montagne Pelée (Martinique)

Poulain

Friant

Mangeney

et al. 2022

Geophysical Journal International

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Summary We investigate the dynamics and deposits of granular flows and the amplitude of landslide-generated water waves using the HySEA depth-averaged shallow-water numerical model, both at laboratory and field scales. We evaluate the different sources of error by quantitatively comparing the simulations with (i) new laboratory experiments of granular collapses in different conditions (dry, immersed, dry flow entering water) and slope angles and (ii) numerical simulations made with the SHALTOP code that describes topography effects better than most depth-averaged landslide-tsunami models. For laboratory configurations, representing the limits of the shallow-water approximation in such models, we show that topography and non-hydrostatic effects are crucial. When topography effects are accounted for empirically—by artificially increasing the friction coefficient and performing non-hydrostatic simulations—the model is able to reproduce the granular mass deposit and the waves recorded at gauges located at a distance of more than 2–3 times the characteristic dimension of the slide with an error ranging from 1 per cent to 25 per cent depending on the scenario, without any further calibration. Taking into account this error estimate, we simulate landslides that occurred on Montagne Pelée volcano, Martinique, Lesser Antilles as well as the generated waves. Multiple collapse simulations support the assumption that large flank collapses on Montagne Pelée likely occurred in several successive sub-events. This result has a strong impact on the amplitude of the generated waves and thus on the associated hazards. In the context of the ongoing seismic volcanic unrest at Montagne Pelée volcano, we calculate the debris avalanche and associated tsunamis for two potential flank-collapse scenarios.

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Dilatancy in dry granular flows with a compressible μ(I) rheology

Cited by 12 publications

References 39 publications

The influence of gas pore pressure in dense granular flows: numerical simulations versus experiments and implications for pyroclastic density currents

The influence of gas pore pressure in dense granular flows: numerical simulations versus experiments and implications for pyroclastic density currents

Effect of fluidization in increasing the run-out distance of granular flows generated from different aspect ratio collapsing columns

Performance and limits of a shallow-water model for landslide-generated tsunamis: from laboratory experiments to simulations of flank collapses at Montagne Pelée (Martinique)

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