Deposition morphology in large-scale laboratory stony debris flows

Baselt, Ivo; Oliveira, Gustavo Queiroz de; Fischer, Jan-Thomas; Pudasaini, Shiva P.

doi:10.1016/j.geomorph.2021.107992

Cited by 17 publications

(23 citation statements)

References 85 publications

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“…This term vanishes at the free surface. Second, (∇ • (u f − u s )) 1 2 η (h − η) is quadratic in η, but has a special form. Such term with factor η (h − η) does not appear in other contributions in τ zzs .…”

Section: Effective Normal Loadsmentioning

confidence: 99%

A Non-Hydrostatic Multi-Phase Mass Flow Model

Pudasaini¹

2022

Preprint

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Modeling mass flows is classically based on the hydrostatic, depth-averaged balance equations. However, if the momentum transfers scale similarly in the slope parallel and the flow depth directions, then the gravity and the acceleration can have the same order of magnitude effects. This urges for a non-hydrostatic model formulation. Here, we extend existing single-phase Boussinesq-type gravity wave models by developing a new non-hydrostatic model for multi-phase mass flows consisting of the solid and fine-solid particles, and viscous fluid (Pudasaini and Mergili, 2019). The new model includes enhanced gravity and dispersion effects taking into account the interfacial momentum transfers due to the multi-phase nature of the mass flow. We outline the fundamentally new contributions in the non-hydrostatic Boussinesq-type multi-phase gravity waves emerging from the phase-interactions including buoyancy, drag, virtual mass and Newtonian as well as non-Newtonian viscous effects. So, this contribution presents a more general, well-structured framework of the multi-phase flows with enhanced gravity and dispersion effects, setting a foundation for a comprehensive simulation of such flows. We discuss some particular situations where the non-hydrostatic and dispersive effects are more pronounced for multi-phase mass flows. Even the reduced models demonstrate the importance of non-hydrostatic contributions for both the solid and fine solid particles, and the viscous fluid. Analytical solutions are presented for some simple situations demonstrating how the new dispersive model can be reduced to non-dispersive motions, yet largely generalizing the existing non-dispersive models. We postulate a novel, spatially varying dissipative force, called the prime-force, which physically controls the dynamics, run-out and the deposition of the mass flow in a precise way. The practitioners and engineers may find this force very useful in relevant technical applications. This illuminates the need of formally including the prime-force in the momentum balance equation. A simple dispersion equation is derived. We highlight the essence of dispersion on the mass flow dynamics. Dispersion consistently produces a wavy velocity field about the reference state without dispersion. Emergence of such a dispersive wave is the first of this kind for the avalanching debris mass. We reveal that the dispersion intensity increases energetically as the solid volume fraction or the friction decreases.

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Section: Effective Normal Loadsmentioning

confidence: 99%

A Non-Hydrostatic Multi-Phase Mass Flow Model

Pudasaini¹

2022

Preprint

Self Cite

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“…In terms of a geometrical scaling relationship, we compared the relationships between the volumes of the debris flows (V ) and the inundation areas of the sediment deposits (A), similar to De Haas et al (2015b) and Baselt et al (2022) (Fig. 19).…”

Section: Implications For Natural Debris-flow Fansmentioning

confidence: 99%

“…3). However, some dynamic properties, such as flow resistance (Egashira et al, 2001), sediment erosion and entrainment rate (McCoy et al, 2012;De Haas et al, 2022), and flow friction (Pudasaini and Miller, 2013;Lucas 2015), and Baselt et al (2022). Data concerning natural debris flows (n = 323) are from Abele (1974), Li (1983), Crandell et al (1984), Siebert (1984), Francis et al (1985, Siebert et al (1987), Hazlett et al (1991), Hayashi and Self (1992), Siebe et al (1992), Stoopes and Sheridan (1992), Iverson et al (1998Iverson et al ( , 2015, Capra et al (2002), Berti and Simoni (2007), Griswold and Iverson (2008) 2020).…”

Section: Implications For Natural Debris-flow Fansmentioning

confidence: 99%

“…Although the effects of fine sediment (e.g., silt and clay) were intentionally excluded in our experiments to control the hydrograph and the velocity of the debris flows in the flume, fine sediment might alter the resistance and stress structure of natural debris flows (Kaitna et al, 2016;Sakai et al, 2019;Nishiguchi and Uchida, 2022). Because these changes in the resistance and stress of debris flows might affect the rate of separation between the solid and fluid phases (Pudasaini and Fischer, 2020;Baselt et al, 2022), our flume tests could not identify the extent of phase separation on the scale of natural debris flows that comprise wide-ranging sediment particle size from silt to large boulders. In nature, various factors (e.g., phase separation) associated with particle size and grain-size distribution interact, and therefore the behavior of debris flows becomes increasingly complex (e.g., De Haas et al, 2018b).…”

Section: Implications For Natural Debris-flow Fansmentioning

confidence: 99%

“…Debris flows consist of solid (i.e., sediment particles) and fluid (i.e., interstitial water and colloidal sediment particles) phases (Pudasaini and Mergili, 2019;Nishiguchi and Uchida, 2022). When debris flows leave the channel outlet, the relative difference in velocity between the solid and fluid phases increases and leads to phase separation (Pudasaini and Fischer, 2020;Baselt et al, 2022). Around the channel outlet, the solid phase eventually translates into sediment deposition, but the fluid phase continuously descends with the progress of phase separation.…”

Section: Introductionmentioning

confidence: 99%

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Effect of debris-flow sediment grain-size distribution on fan morphology

Tsunetaka

Hotta²,

Sakai³

et al. 2022

Earth Surf. Dynam.

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Abstract. Knowledge of how debris flows result in the fan-shaped morphology around a channel outlet is crucial for mitigation of debris-flow-related disasters and investigation of previous sediment transport from the upper channel. Therefore, using a flume connected to a deposition area (inundation plane), this study conducted fan-morphology experiments to assess the effects of differences in grain-size distribution within debris flows on changes in fan morphology. Two types of debris-flow material, i.e., monogranular particles comprising monodispersed sediment particles and multigranular particles comprising polydispersed sediment particles, were used to generate monogranular and multigranular experimental debris flows, respectively. By adjusting the average grain size coincident between the monogranular and multigranular flows, we generated two types of debris flow with similar debris mixture hydrographs but different grain-size distributions in the flume. Although the flow depths were mostly similar between the monogranular and multigranular flows before the start of the debris-flow runout at the deposition area, the runout distances of the front of the multigranular flows were shorter than those of the monogranular flows. The difference in runout distance was responsible for the variations in the extent to and location in which the debris flows changed their direction of descent, resulting in the different shapes and morphologies of the fans in response to grain-size distribution. Although the direction of descent of the flows changed repeatedly, the extent of morphological symmetry of the debris-flow fans increased at a similar time during fan formation irrespective of the grain-size distribution. In contrast to this similarity in the rate of change in fan symmetry, the shift of the multigranular flow directions eventually increased the extent of asymmetry in fan morphology and expanded the scale of deviations in fan morphology between experimental test runs. Therefore, wide-ranging grain-size distributions within debris flows likely result in complex fan morphology with a high degree of asymmetry.

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Do standing trees affect landslide mobility on forested hillslopes in Japan?

Tsunetaka

Asano

Murakami

2022

Earth Surf Processes Landf

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Landslide mobility likely changes in response to the effects of standing trees on the landslide runout. However, the properties of standing trees that influence landslide runout are not well understood. In this study, the relationships between the properties of landslides and the heights of standing trees and the runout distances of rainfall‐induced landslides (primarily 101–103 m3 in volume) in the Hiroshima Prefecture, Japan, were examined to investigate whether the heights of the trees around the runout area change the landslide mobility. The results indicate that the landslide runout was constrained not only by the landslide area and volume but also by the tree height around the runout area. Tall but sparse standing trees did not prevent landslide runout, whereas dense standing trees resulted in relatively low landslide mobility, irrespective of whether the trees were broadleaf or coniferous. A comparison between our landslide inventory and previously reported landslides showed that the landslide mobility was lower in areas with standing trees than in areas without standing trees, such as under experimental conditions and for landslides in Martian and submarine environments. Therefore, differences in the heights of the trees around the runout area can result in variations in the extent of landslide‐related hazards and disturbances.

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Deposition morphology in large-scale laboratory stony debris flows

Cited by 17 publications

References 85 publications

A Non-Hydrostatic Multi-Phase Mass Flow Model

A Non-Hydrostatic Multi-Phase Mass Flow Model

Effect of debris-flow sediment grain-size distribution on fan morphology

Do standing trees affect landslide mobility on forested hillslopes in Japan?

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