Load–deflection of flexible ring-net barrier in resisting debris flows

Quantitative understanding of the load–deflection mechanisms of a flexible barrier in intercepting debris flows is critical for barrier design, but remains practically challenging due to the difficulties involved in capturing multi-phase, multi-way interactions. This study employs a physics-based coupled computational fluid dynamics and discrete-element method (CFD–DEM) to simulate a flexible ring-net barrier as a permeable, deformable multi-component system by DEM and model a debris flow as a mixture of discrete particles and a continuous slurry by DEM and CFD, respectively. The CFD–DEM coupling framework offers a unified treatment of in-flow solid–fluid interaction, flow–barrier interaction and interactions among barrier components. Numerical predictions of key flow–barrier interactions and cable forces show reasonable consistency with large-scale experiments. Systematic simulations with varying flow–barrier height ratios ε and flow dynamics are performed to examine the evolving mechanisms of load sharing and transmission and quantify the ε-dependent load–deflection modes. The ratio ε is found to bear a strong, positive correlation with the key barrier response in three typical modes. The post-peak barrier deformations experience shrinkages with ε ≤0·6 and expansions when ε . 0·6. This study helps to improve understanding of the load–deflection mechanisms for practical design of flexible barriers in mitigating debris flows.