Plasticity and geophysical flows: A review

By C. Ancey. 2007

438 citations recorded by the source corpus.

The objective of this review is to examine how the concept of plasticity is used in geophysical fluid dynamics. Rapid mass movements such as snow avalanches or debris flows involve slurries of solid particles (ice, boulder, clay, etc.) within an interstitial fluid (air, water). The bulk behavior of these materials has often been modeled as plastic materials, i.e., a plastic material yields and starts to flow once its stress state has significantly departed from equilibrium. Two plastic theories are of common use in fluid dynamics: Coulomb plasticity and viscoplasticity. These theories have little in common, since ideal Coulomb materials are two-phase materials for which pore pressure and friction play the key role in the bulk dynamics, whereas viscoplastic materials (e.g., Bingham fluids) typically behave as single-phase fluids on the macroscopic scale and exhibit a viscous behavior after yielding. Determining the rheological behavior of geophysical materials remains difficult because they encompass coarse, irregular particles over a very wide range of size. Consequently, the true nature of plastic behavior for geophysical flows is still vigorously debated. In this review, we first set out the continuum-mechanics principles used for describing plastic behavior. The notion of yield surface rather than yield stress is emphasized in order to better understand how tensorial constitutive equations can be derived from experimental data. The notion of single-phase or two-phase behaviors on the macroscopic scale is then examined using a microstructural analysis on idealized suspensions of spheres within a Newtonian fluid; for these suspensions, the single-phase approximation is valid only at very high or low Stokes numbers. Within this framework, the bulk stress tensor can also be constructed, which makes it possible to give a physical interpretation to yield stress. Most of the time, depending on the bulk properties (especially, particle size) and flow features, bulk behavior is either Coulomb-like or viscoplastic in simple-shear experiments. The consequences of the rheological properties on the flow features are also examined. Some remarkable properties of the governing equations describing thin layers flowing down inclined surfaces are discussed. Finally, the question of parameter fitting is tackled: since rheological properties cannot be measured directly in most cases, they must be evaluated from field data. As an example, we show that the Coulomb model successfully captures the main traits of avalanche motion, but statistical analysis demonstrates that the probability distribution of the friction coefficient is not universal.

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Citations in the corpus

Refractive-index and density matching in concentrated particle suspensions: a review (2011, background): “…gravity-driven geophysical flows such as snow avalanches, debris flows, turbidity currents, pyroclastic flows, etc. Industrial pastes such as drilling muds, concrete, cosmetic pastes, pharmaceutical pastes, composites or foodstuffs offer other examples of particulate suspensions (Ancey 2007).”
Yielding to Stress: Recent Developments in Viscoplastic Fluid Mechanics (2014, background): “Ancey (2007) reviewed notable geophysical applications, and Mitsoulis (2007) summarized many industrial applications and simulation studies.”
Numerical modeling of 2‐D granular step collapse on erodible and nonerodible surface (2009, methodology): “[3] Numerical simulations of natural mass flows over complex terrains are currently used and developed to assess hazard and risk in exposed areas [Iverson and Denlinger, 2001; Denlinger and Iverson, 2001, 2004; Mangeney et al., 2000; Mangeney-Castelnau et al., 2005; Hungr, 1995; Chen and Lee, 2000; ”
Measuring the plasticity of clays: A review (2011, unknown): “In the last century, the work of Mohr served as a base of some concepts currently used such as elastic and plastic deformation, yielding (critical state), shear localization and post-failure behavior (Ancey, 2007).”
Determination of clay plasticity: Indentation method versus Pfefferkorn method (2008, unknown): “), calcium minerals (mainly calcite) and silica (Peters, 1991; Ancey, 2007).”