Multiphysics and Multiscale Modeling of Bouldery Debris Flow Interactions with Baffles and Slit Dam

Abstract

Debris flow is a channelized flow-type landslide that pose significant risks to infrastructures and human life due to its high-velocity slurry and impact forces from entrained boulders. Realistic numerical modeling of debris flow remains challenging, as it involves multiscale interactions between different phases (e.g., boulders, soil, slurry, and water) and multiphysics processes (e.g., fluid-particle and debris-structure interaction). This study introduces two advanced numerical frameworks to unravel the impact mechanism of bouldery debris flows on debris-resisting structures: 1) a fully resolved smoothed particle hydrodynamics-discrete element method (SPH-DEM) coupling model, and 2) a two-level discrete element method (2L-DEM). Both approaches explicitly resolve the multiphase nature of debris flows by treating boulders and fine-grained slurry as distinct interacting phases, enabling previse quantification of momentum transfer, energy dissipation, and structural responses. The SPH-DEM captures fluid-driven boulder dynamics and backflow effects around baffles, while the 2L-DEM captures granular jamming and force redistribution in the impact process on slit dam. The simulation results demonstrate that the formation of bouldery front and viscosity of slurry significantly alter the impact regimes on baffles, whereas the relative size of particle and slit dam aperture critically governs the debris retention efficiency. By bridging microscale particle interactions to macroscale flow-structure behavior, this work provides physics-based insights for optimizing debris-resisting structures, offering geotechnical engineers validated tools to enhanced hazard mitigation strategies on key infrastructure near mountainous region.