Debris Flows, Boulders and Constrictions: A Simple Framework for Modeling Jamming, and Its Consequences on Outflow

Abstract

Debris flows contain mixtures of fluids and large boulders. These mixtures can pass through constrictions, either man-made or natural, for example, structures such as slit-dams, open check dams and sabō dams (hereafter all referred to using the umbrella term of "slit-dams"), or canyons and gullies (e.g., Hübl & Fiebiger, 2005;Rudolf-Miklau & Suda, 2013;Shima et al., 2016). In all cases, the flow rates of sediments and fluids are affected by both horizontal and vertical constrictions. Boulders that are larger than the constriction size are certainly jammed, whilst smaller boulders may become jammed if they approach the constriction as a group (Figure 1). This jamming can be used advantageously for slit-dams in areas where large-scale debris flows can occur. During small-scale routine events, where boulders are sparse, jamming ought not to occur. This minimizes the need for

Influence of the solid fraction on the clogging by bridging of suspensions in constricted channels

“…The flow of suspended particles can often lead to clogging in confined systems at various scales, from blood vessels 1,2 and porous media, 3,4 to pipes 5 and canyons. 6 Clog formation remains a major issue in many technological applications, whether it is in irrigation, [7][8][9][10] filtration, 11,12 flood prevention, 13 3D printing, 14,15 biopharmaceutical manufacturing, 16 or microfluidic devices. [17][18][19] Constrictions in channels are weak points for clogging in such systems since the cross-section of the channel suddenly reduces.…”

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Bi‐Linear Laws Govern the Impacts of Debris Flows, Debris Avalanches, and Rock Avalanches on Flexible Barrier

“…On the other hand, the barrier ring net size (i.e., ring diameter equal to 0.07 m) is determined to retain large particles ($${d}_{\mathrm{p}}$$ = 0.08 m) in a flow while allowing small particles ($${d}_{\mathrm{p}}$$ = 0.04 or 0.06 m) to pass through, which recovers the primary function of a real‐world flexible barrier. In addition to solid volume concentrations and flow dynamics, the flow‐barrier interactions can also be affected by the complex natures of geophysical flows, including varying flow depths (Faug et al., 2012; Iverson et al., 2016), broad particle size distributions (Cabrera & Estrada, 2021), large boulders (Belli et al., 2022; Piton et al., 2022), phase separation of the solid and fluid components (Leonardi et al., 2015; Pudasaini & Fischer, 2020), and erosion (Berger et al., 2011; Pudasaini & Krautblatter, 2021). Meanwhile, the barrier geometry and configuration (e.g., barrier width and height, number of horizontal supporting cables, and the ring‐to‐largest particle size ratio) may also affect the results presented in the following sections.…”

Jammed and Mobilized Domains in Debris Flow, Debris Avalanche and Rock Avalanche against Slit-check Dams

“…solid-liquid nature, wide ranges of Froude-number and particle size distributions) and simultaneous multiple processes (e.g. flow reduction and separation, debris jamming, filtering, and overtopping) limit rational studies to simplified models (Piton et al, 2022). Also, owing to this complexity, the design of the most suitable structure is, however, problematic.…”

“…Existing studies on the impact behavior of geophysical flows against slit-check dams mainly rely on theoretical, small-scale physical, and numerical analysis. However, the aforementioned complexity also goes beyond the limits of the validity of hydraulic formulas (Armanini & Larcher, 2001) or theoretical predictions (Piton et al, 2022). Moreover, the majority of physical studies focused on the hydraulic conditions or lack quantitative indices for evaluating the trapping, overspreading and energy-breaking efficiencies (Armanini & Larcher, 2001;Rossi & Armanini, 2019).…”