Abstract The $\mu (I)$ -rheology is a nonlinear viscous law, with strain-rate invariant and pressure-dependent viscosity, that has proved to be effective at modelling dry granular flows in the intermediate range of inertial number, $I$ . This paper shows how incorporate rheology into depth-averaged avalanche models. To leading order, generates an basal friction, which equivalent rough bed friction law. A viscous-like term can derived by integrating in-plane deviatoric stress through depth,...

Abstract Debris flows can spontaneously develop regular large-amplitude surge waves that are interspersed by periods in which the channel fill is completely stationary. These important because each individual much more destructive than a steady uniform flow with same mass flux. In this paper small-scale experiments exhibit similar behaviour described. The consists of carborundum particles down rough inclined chute covered static erodible layer grains. For inflow conditions close to minimum...

Geophysical granular flows, such as avalanches, debris lahars and pyroclastic are always strongly influenced by the basal topography that they flow over. In particular, localised bumps or obstacles can generate rapid changes in thickness velocity, shock waves, which dissipate significant amounts of energy. Understanding how a material is affected underlying therefore crucial for hazard mitigation purposes, example to improve design deflecting catching dams snow avalanches. Moreover,...

Snow avalanches are typically initiated on marginally stable slopes with a surface layer of fresh snow that may easily be incorporated into them. The erosion at the front is fundamental to dynamics and growth they rapidly bulk up, making them much more destructive than initial release. also deposit rear, base sides flow net balance deposition determines whether an avalanche grows or decays. In this paper, small-scale analogue experiments performed rough inclined plane static erodible...

Geophysical mass flows such as debris flows, dense pyroclastic and snow avalanches can self-channelize on shallow slopes. The confinement afforded by formed levees helps to maintain the flow depth, hence mobility, allowing self-channelized run out significantly farther than unconfined, spreading flows. Levee formation self-channelization are strongly associated with particle-size segregation, but also occur in monodisperse This paper uses depth-averaged theory of Rocha et al. ( J. Fluid...

We study a system in which granular matter, flowing down an inclined chute with periodic boundary conditions, organizes itself train of roll waves varying size. Since large travel faster than small ones, the merge, and their number gradually diminishes. This coarsening process, however, does not generally proceed to ultimate one-wave state: Numerical simulations dynamical equations (being analogue shallow water equations) reveal that process is arrested at some intermediate stage. confirmed...

Shallow granular avalanches on slopes close to repose exhibit hysteretic behaviour. For instance, when a steady-uniform flow is brought rest it leaves deposit of thickness $h_{stop}(\unicode[STIX]{x1D701})$ rough slope inclined at an angle $\unicode[STIX]{x1D701}$ the horizontal. However, this layer will not spontaneously start again until higher $\unicode[STIX]{x1D701}_{start}$ , or increased $h_{start}(\unicode[STIX]{x1D701})>h_{stop}(\unicode[STIX]{x1D701})$ . This simple phenomenology...

Abstract

When a layer of static grains on sufficiently steep slope is disturbed, an upslope-propagating erosion wave, or retrogressive failure, may form that separates the initially material from downslope region flowing grains. This paper shows relatively simple depth-averaged avalanche model with frictional hysteresis sufficient to capture planar failure independent cross-slope coordinate. The modelled non-monotonic effective basal friction law has static, intermediate (velocity decreasing) and...

The effect of particle size segregation in an upslope propagating, bidisperse granular bore is investigated and experimental observations agree with recent progress that upwards downwards large small particles, respectively, asymmetric.

A continuous exchange of particles between an erodible substrate and the granular flow above it occurs during almost all geophysical events involving material, such as snow avalanches, debris flows pyroclastic flows. The balance eroded deposited material can drastically influence runout distance duration flow. In certain conditions, a perfect erosion deposition may occur, leading to steady propagation in which maintains its shape velocity throughout. It is shown experimentally how...

De par le vaste champ d’applications qu’elle offre, l’étude des écoulements granulaires a connu une expansion considérable au cours de ces vingt dernières années, autant du point vue industriel que géophysique. Ces ont grande influence dans monde qui nous entoure. Or, différentes instabilités hydrodynamiques peuvent naitre en leur sein, entrainant alors changements importants propriétés mêmes l’écoulement. Les dues à la ségrégation taille particules, développement d’ondes surface ou encore...