Empirical and analytical analyses of laboratory granular flows to investigate rock avalanche propagation

Manzella, Irene; Labiouse, V.

doi:10.1007/s10346-011-0313-5

Cited by 72 publications

(40 citation statements)

References 39 publications

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“…Of variables not tested, the fall height, which also determines the value of

scriptF

, is expected to control the travel distance. Also, the angle of the slope, as well as the shape of the transition between the plates, can be expected to play a significant role [e.g., Manzella and Labiouse , ]. In particular, these variables not only have a direct effect on the travel length but also on the degree of fragmentation, which in turn affects the travel distance of the center of mass.…”

Section: Discussionsupporting

confidence: 91%

On the energy budgets of fragmenting rockfalls and rockslides: Insights from experiments

et al. 2016

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The travel lengths of rockfalls and rockslides can be difficult to predict due to complex interactions of numerous physical processes, such as fragmentation of the rock mass and its effect on the energy dissipation through basal and internal friction. Previous studies have shown that the front of the rockslide deposits travels farther with increased fragmentation. However, little is known about the displacement of the center of mass, which is the relevant parameter for studying the energy budget, leaving open the question whether fragmentation acts as an effective sink or source of energy. Taking advantage of a newly developed rock analogue material, we perform a total of 109 experiments to study the effect of fragmentation on the displacement of the center of mass and the energy budget of experimental rockslides. To determine the degree of fragmentation, we define a characteristic fragment size from the total mass of the experimental sample and the mass of the largest fragment. The degree of fragmentation is seen to depend linearly on the aspect ratio of the experimental sample and as a power law on its cohesion. Similar to the previous studies, our results show that the travel distance of the front of the deposits increases with the degree of fragmentation. In contrast, displacement of the center of mass is reduced with the degree of fragmentation, suggesting increased energy consumption, consistent with the assumption that fragmentation acts effectively as an energy sink.

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“…Of variables not tested, the fall height, which also determines the value of

scriptF

Section: Discussionsupporting

confidence: 91%

On the energy budgets of fragmenting rockfalls and rockslides: Insights from experiments

et al. 2016

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“…Likely due to the shape and the granular nature of the deposits, rock avalanches are often modelled as granular flows both in analogue (Davies and McSaveney 1999;Iverson et al 2004;Shea and van Wyk de Vries 2008;Dufresne 2012;Manzella and Labiouse 2012) and numerical (Campbell et al 1995;Mollon et al 2012) experiments. However, using granular material to model rock avalanches means assuming that dynamic fragmentation is negligible, i.e., one assumes that the rocks instantaneously disintegrate after detachment and that no further fragmentation occurs during the travel.…”

Section: Introductionmentioning

confidence: 99%

Modelling Fragmentation in Rock Avalanches

Haug¹,

Rosenau²,

Leever³

et al. 2014

Landslide Science for a Safer Geoenvironment

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The physical description of rock masses travelling down a slope is a complex problem, involving bouncing, rolling, sliding, flowing, fracturing and/or combinations of these. Modelling serves as a valuable tool to study these systems which are rarely monitored at high resolution in nature. Often, granular models (e.g. loose sand) are used to study rock avalanches in experimental simulations. For such granular models, one has to assume that the rock mass disintegrates instantaneously after detachment and that fragment size does not reduce further during the movement. We present a new method that overcomes this limitation by simulating dynamically fragmenting gravitational mass movements.We have developed a material that fails in a brittle manner at lab scale conditions. The material is produced by cementing sand with gypsum (anhydrite) or potato starch, which allows controlling the shear strength over a wide range. Experiments are performed by releasing the material down a slope and monitoring with a digital camera at frequencies of 50 or 250 Hz. Two techniques are used to quantify the experimental results: particle image velocimetry which quantifies the surface velocity field, and optical image analysis to derive geometric (e.g. fragment size distribution) and mechanical properties (e.g. basal friction) of the model.Preliminary results from the experiments illustrate the different dynamics of the gravitational mass movement as a function of shear strength.

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“…Okura et al (2000) obtained this effect on a laterally unconfined planar slope ending on a horizontal depositional plane with no lateral constraints. With such sharp breaks in slope, the larger the decrease in the slope inclination angle, the larger the energy dissipation of the flow (Manzella and Labiouse, 2013). In nature, the flank of a volcano provides an instance of a gradual change in the slope inclination angle (besides the flanks of Mayon Volcano, other examples illustrated in the literature are those of Mount Ngauruhoe (Lube et al, 2007) and Volcán de Colima (Saucedo et al, 2002)), whereas the intersection of a mountainside with an alluvial plain is an example of an abrupt change in the slope inclination angle.…”

Section: Flow Volume Effect On Flow Mobilitymentioning

confidence: 99%

Combined effects of grain size, flow volume and channel width on geophysical flow mobility: three-dimensional discrete element modeling of dry and dense flows of angular rock fragments

Cagnoli

Piersanti

2017

Solid Earth

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Abstract. We have carried out new three-dimensional numerical simulations by using a discrete element method (DEM) to study the mobility of dry granular flows of angular rock fragments. These simulations are relevant for geophysical flows such as rock avalanches and pyroclastic flows. The model is validated by previous laboratory experiments. We confirm that (1) the finer the grain size, the larger the mobility of the center of mass of granular flows; (2) the smaller the flow volume, the larger the mobility of the center of mass of granular flows and (3) the wider the channel, the larger the mobility of the center of mass of granular flows. The grain size effect is due to the fact that finer grain size flows dissipate intrinsically less energy. This volume effect is the opposite of that experienced by the flow fronts. The original contribution of this paper consists of providing a comparison of the mobility of granular flows in six channels with a different cross section each. This results in a new scaling parameter χ that has the product of grain size and the cubic root of flow volume as the numerator and the product of channel width and flow length as the denominator. The linear correlation between the reciprocal of mobility and parameter χ is statistically highly significant. Parameter χ confirms that the mobility of the center of mass of granular flows is an increasing function of the ratio of the number of fragments per unit of flow mass to the total number of fragments in the flow. These are two characteristic numbers of particles whose effect on mobility is scale invariant.

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Empirical and analytical analyses of laboratory granular flows to investigate rock avalanche propagation

Cited by 72 publications

References 39 publications

On the energy budgets of fragmenting rockfalls and rockslides: Insights from experiments

On the energy budgets of fragmenting rockfalls and rockslides: Insights from experiments

Modelling Fragmentation in Rock Avalanches

Combined effects of grain size, flow volume and channel width on geophysical flow mobility: three-dimensional discrete element modeling of dry and dense flows of angular rock fragments

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