The effect of porosity in a row of barriers on mitigation of flow dynamics and barrier interaction: Viscoplastic debris flows in a flume

Viscoplastic debris flows, characterized by a finite yield stress and plastic viscosity, pose serious threats to infrastructure and communities in mountainous and flood-prone regions. Engineered barriers are commonly deployed to reduce flow velocity, trap sediments, and dissipate kinetic energy. Yet, the influence of barrier porosity and channel slope on the behavior of viscoplastic debris flows is not well understood, limiting optimized design strategies. This study employs three-dimensional Computational Fluid Dynamics simulations of dam-break-driven viscoplastic debris flows to investigate the effects of porosity in a single row of uniform barriers. Porosity, defined as the spacing between barriers of fixed geometry, varies from ϕ=0.3 to 0.9. The impact of channel inclination is also examined for θ=0°, 5°, 15°, 30°, and 45°, enabling assessment of flow redirection and force attenuation. Analyses of velocity fields, pressure distributions, and shear stresses provide detailed insights into fluid–structure interactions. Results show that both porosity and slope strongly control flow dynamics and energy dissipation. The runout length of viscoplastic flows decreases significantly with decreasing porosity, with reductions of up to tenfold between ϕ=1 and ϕ=0.3. Lower porosities elevate barrier forces while reducing downstream wall loads, whereas steeper slopes consistently amplify forces on barriers and end walls. At ϕ=0.3–0.4, stagnant, unyielded zones develop, generating localized stresses tracked over time. These findings offer critical guidance for designing barrier systems, supporting more effective mitigation of debris flows, landslides, and associated natural hazards.