Quantifying the impact of a debris avalanche against a flexible barrier by coupled DEM-FEM analyses
Flexible barriers are an effective type of mitigation measure against debris avalanches in valleys and can affect the kinetic energy and mass of debris avalanches. To investigate the complex dynamic interaction between a debris avalanche and a flexible barrier, a modeling framework was developed based on coupled discrete element method (DEM) and finite element method (FEM). The debris avalanche was modeled as an assembly of discrete particles accounting for collision–friction effect, and the flexible barrier was modeled by applying the FEM accounting for connections and contact in a realistic manner. The coupled numerical model was well validated by comparing the numerical results with experimental data reported in the literature. This model was employed to examine the dynamics of debris avalanche–barrier interaction, such as the interaction process, impact force, energy dissipation mechanism, and evolution of the internal forces of the components, as well as the influences of the bulk density and impact height of the debris avalanche and the slope angle of the channel on the coupled impact force. Based on the numerical results, three interaction stages were identified, namely, frontal impact, run-up, and pile-up. During the interaction process, the effects of run-up and dead zone formation need to be accounted to avoid conservative estimates of the impact force. The analyses of the energy transformation showed that 76.2% of the initial total energy was dissipated by interaction friction, and the flexible barriers may mainly focus on the frontal impact energy of the debris avalanche by using an energy design approach. The sensitivities of the bulk density, impact height, and slope angle on the maximum impact force are 1, 0.186, and 2.084, respectively. The parameters with high sensitivity are the main influencing parameters and should be given priority in the design of flexible barriers.
Keywords: Flexible barriers, Debris avalanche, Coupled DEM-FEM model, Dynamic interaction, Sensitivity analysis