Flexible barriers made of cable-supported nets are used to protect against gravity-driven natural hazards such as rockfalls, debris flows, snow avalanches, shallow landslides, and woody debris. The main design and research priority is to ensure these barriers perform as designed. Differing from rigid barriers, the interconnected components of these flexible barriers allow for site-specific design. Existing research on the use of these barriers in rain torrents has mainly focused on the load exerted by the debris flow and the resulting loads within the barrier. Up to now, issues related to optimizing mesh size and the influence of barrier flexibility and flow run-up have been addressed to a lesser extent. Lab experiments on barrier models are a cost-saving alternative to address the flexible barrier response and its effect on the flow given the many variables and scale of this type of research. 

Researchers Stéphane Lambert, Franck Bourrier, Ana Rocio Ceron-Mayer, Loïc Dugelas, Fabien Dubois, and Guillaume Piton, propose a way to design small-scale barriers with geometrical and mechanical characteristics similar to real-scale barriers. The researchers used flume experiments to investigate how effectively a flexible barrier contains torrential-flow-driven solid materials, along with 3D printing to manufacture barrier components, and discrete element modeling to simulate the response of the barriers. Their paper, “Small-Scale Modeling of Flexible Barriers. I: Mechanical Similitude of the Structure” in the Journal of Hydraulic Engineering, addresses how to achieve the partial mechanical similitude of manufactured flexible barriers. Learn more about this research at https://doi.org/10.1061/JHEND8.HYENG-13070. The abstract is below.


Flexible barriers can be used to trap woody debris or debris flows. However, their small scale modelling is challenging because of their possible deformation. This article addresses how to meet the partial mechanical similitude of manufactured flexible barriers. Relevant dimensionless parameters are defined from flow velocity, barrier geometry, and component mechanical properties. These similitude criteria are validated using numerical simulations of barriers exposed to a hydrodynamic loading at various scales. The simulations also confirm the importance of accounting for the mechanical characteristics of the barrier components when designing model barriers in view of achieving realistic deformations. Next, a real barrier with complex features is scaled to conduct flume experiments. This scaled barrier is 3D-printed with material selected to achieve the mechanical similitude criterion. Another validation of this approach is performed considering hydrostatic loading and checking that simulated and measured deformations are similar. As an application case, the deformations measured during the experiments performed with woody debris are also compared to the hydrostatic loading.

See more on how to enhance flexible barriers in the paper in ASCE Library: https://doi.org/10.1061/JHEND8.HYENG-13070.