Particle–Fluid–Structure Interaction for Debris Flow Impact on Flexible Barriers

Flexible barriers are increasingly used for the protection from debris flow in mountainous terrain due to their low cost and environmental impact. How- ever, the development of a numerical tool for the ratio- nal design of such structures is still a challenge. In this work, a hybrid computational framework is presented, using a total Lagrangian formulation of the finite element method to represent aflexible barrier. The actions exerted on the structure by a debris flow are obtained from si- multaneous simulations of the flow of a fluid-grain mix- ture, using two conveniently coupled solvers: the discrete element method governs the motion of the grains, while the free-surface non-Newtonian fluid phase is solved us- ing the lattice Boltzmann method. Simulations on real- istic geometries show the dependence of the momentum transfer on the barrier on the composition of the debris flow, challenging typical assumptions made during the design process today. In particular, we demonstrate that both grains and fluid contribute in a nonnegligible way to the momentum transfer. Moreover, we show how the flexibility of the barrier reduces its vulnerability to struc- tural collapse, and how the stress is distributed on its fabric, highlighting potential weak points.