3D numerical simulation of debris-flow motion using SPH method incorporating non-Newtonian fluid behavior

Flow-type landslide, such as debris-flow, often exhibits high velocity and long run-out distance. Simulation on it benefits the propagation analysis and provides solution for risk assessment and mitigation design. Previous studies commonly used shallow water assumption to simulate this phenomenon, ignoring the information in vertical direction, and the Bingham model to describe constitutive law of non-Newtonian fluid can cause numerical divergence unless necessary parameter is defined. To address the issue, the full Navier-Stokes equations are adopted to describe the dynamics of the flow-type landslides. Additionally, the general Cross model is employed as the constitutive model, which ensures the numerical convergence. Rheological parameters are introduced from the Bingham model and the Mohr-Coulomb yield criterion. Subsequently, the governing equations incorporating the modified rheological model are numerically built in the smoothed particle hydrodynamics (SPH) framework and implemented into the open-source DualSPHysics code. To illustrate its performance, the 2010 Yohutagawa debris-flow event in Japan is selected as a case study. Parameters regarding the debris magnitude, i.e., the front velocity and section discharge, were also well analyzed. Simulated mass volume and deposition depth at the alluvial fan are in good agreements with the in situ observation. On the basis of the results, the developed method performs well to reproduce the debris-flow process and also benefits the analysis of flow characteristics, affected area for risk assessment and mitigation design.