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

• Published in: Journal of geophysical research. Earth surface 2022-11, Vol.127 (11), p.n/a
• Main Authors: Kong, Yong, Guan, Mingfu, Li, Xingyue, Zhao, Jidong, Yan, Haochen
• Format: Article
• Language: English
• Subjects: Avalanches; Dead loads; Debris flow; debris flows; Deformation; Design factors; Detritus; Field investigations; Field tests; flexible barrier system; Flow distribution; Flow pattern; fluid‐solid modeling; Forces; Froude number; Geological hazards; Geophysical methods; Geophysics; impact dynamics; Impact loads; Inflection points; Landslides; Mass flow; Methods; Multiphase; multiphase multiway interactions; Numerical prediction; Peak load; Physics; Rock; rock avalanches; Rock falls; Rockfall; Rocks; Snow avalanches
• ISSN: 2169-9003; 2169-9011
• DOI: 10.1029/2022JF006870

Geophysical mass flows impacting flexible barriers can create complex flow patterns and multiway solid‐fluid‐structure interactions, wherein estimates of impact loads rely predominantly on analytical or simplified solutions. However, an examination of the fundamental relations, applicability, and underlying mechanisms of these solutions has been so far elusive. Here, using a coupled continuum‐discrete method, we systematically examine the physical laws of multiphase, multiway interactions between geophysical flows of variable natures, and a permeable flexible ring net barrier system. This model well captures the essential physics observed in experiments and field investigations. Our results reveal for the first time that unified bi‐linear laws underpin widely used analytical and simplified solutions, with inflection points caused by the transitions from trapezoid‐shaped to triangle‐shaped dead zones. Specifically, the peak impact load increases bi‐linearly with increasing Froude number, peak cable force, or maximum barrier deformation. Flow materials (wet vs. dry) and impact dynamics (slow vs. fast) jointly drive the patterns of identified bi‐linear correlations. These findings offer a physics‐based, significant improvement over existing solutions to impact problems for geophysical flows. Plain Language Summary Flexible barriers are increasingly used worldwide to mitigate debris flows, debris/rock/snow avalanches, and rockfalls. Although many methods exist to estimate critical design factors of flexible barriers, a systematic examination of their applicability and underlying relations remains elusive. The status quo has been largely caused by the challenges of capturing and quantifying the multiphase, multiway flow‐barrier interactions. Here, we perform a series of hybrid solid‐fluid simulations to explore the impact of debris flows/avalanches and rock avalanches on a flexible barrier system. Our numerical predictions of critical physical processes show reasonable consistency with experimental and field observations. For the first time, the physics‐based numerical measures of the flow‐barrier forces, in‐barrier forces, and barrier load‐deformation relations reveal the unified bi‐linear laws behind widely used methods. We find that the flow‐specific turning points of the bi‐linear laws are due to the changes from trapezoid‐shaped to triangle‐shaped jammed regions formed upstream of the barrier. Our findings quantitatively explain how flow properties (e.g.,