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

Abstract

Flexible barriers are increasingly used for the protection from debris flow in mountainous terrain due to their low cost and environmental impact. However, a numerical tool for rational design of such structures is still missing. In this work, a hybrid computational framework is presented, using a total Lagrangian formulation of the Finite Element Method (FEM) to represent a flexible barrier. The actions exerted on the structure by a debris flow are obtained from simultaneous simulations of the flow of a fluid-grain mixture, using two conveniently coupled solvers: the Discrete Element Method (DEM) governs the motion of the grains, while the freesurface non-Newtonian fluid phase is solved using the Lattice-Boltzmann Method (LBM). Simulations on realistic 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 non-negligible way to the momentum transfer. Moreover, we show how the flexibility of the barrier reduces its vulnerability to structural collapse, and how the stress is distributed on its fabric, highlighting potential weak points.

A coupled 3‐dimensional bonded discrete element and lattice Boltzmann method for fluid‐solid coupling in cohesive geomaterials

“…The hydrodynamic forces at the moving boundary are accomplished by introducing an additional collision term for nodes covered partially or fully by the solid and a weighting function involving the solid fraction within a computational cell. Because of its precise representation of the particle boundary, well computational stability, and efficiency, the IMB has been widely used in the coupled DEM‐LBM technique where a few thousand particles immersed in the fluid can be considered . The immersed boundary (IB) scheme, the last approach, was introduced to the lattice Boltzmann method by Feng and Michaelides and examined by a couple of researchers .…”

“…The macroscopic behaviour is obtained by resolving the microscopic/mesoscopic interparticle forces in discrete element method (DEM). The fluid‐solid coupling and fluid flow in pores can be approached by the mesoscopic particle‐based methods, such as smoothed particle hydrodynamics (SPH) and lattice Boltzmann method (LBM) . In these fluid solvers, the governing equations of fluid flow are algebraic equations rather than differential equations.…”

A unified CFD‐DEM approach for modeling of debris flow impacts on flexible barriers

“…Compared with traditional rigid barriers, flexible barriers are easy and economical for installations and replacements, especially in inaccessible mountainous regions where debris flows occur frequently. In urban areas, flexible barriers are also popular for debris‐resisting since their presence is not excessively intrusive for the surrounding environment . Although the design of rigid barriers has accumulated rich engineering experience, it cannot be directly applied to the design of flexible barriers, due to totally different mechanical characteristics of the two.…”

“…No firm guidelines built upon sounded theoretical basis are available for flexible barrier design. Only limited experimental and numerical studies have been reported recently . Reliable characterization and modeling of debris flow and its impacts on a flexible barrier hinge on realistic consideration of the three‐way coupling and interactions among the debris fluid, the debris solid and the flexible barrier structure.…”

Experimental Study on the Performance of Polyurethane-Steel Sandwich Structure under Debris Flow

“…To attenuate the dynamic impact force generated by debris flow and mitigate the subsequent destructive effects, many debris flow prevention and control engineering, such as debris flow barriers, debris racks and fences, debris-flow retention structures and debris breakers [26][27][28][29][30], are applied. Nevertheless, present design of these structures usually refers to empirical models [31].…”