Numerical study on collapse of saturated soil columns based on two-layer two-phase smoothed particle hydrodynamics

： Solid-liquid two-phase flow generally occurs during natural disasters ， such as debris flows and avalanches. To address the shortcomings of current numerical methods，this study developed a two-layer two-phase smoothed particle hydrodynamics(SPH) method by combining soil constitutive equations and considering the complex interaction mechanism between the solid and liquid phases. The simulation of soil-water interaction with large deformation is performed using unified governing equations under the framework of the continuous medium theory，revealing its practical feasibility for researching large-scale debris flows. The accuracy and reliability of the developed numerical method for modeling the liquid and soil motion，as well as the interaction of soil-water are verified through a numerical example of saturated soil collapse in air，which approximates actual debris flows. The sensitivity analysis of fluid viscosity，effective grain size of soil mass，initial void ratio，and other parameters was conducted. Meanwhile，different percolation models for the soil-water coupling are compared. The results suggest that the proposed two-layer two-phase SPH method in this paper is reasonable and effective for simulating the soil-water coupling with large deformation. Notably，the environmental liquid and soil parameters significantly affect the results. When the Reynolds number of the particles is large，percolation models are essential for correctly simulating the interaction between solid and liquid and capturing the interface between the two phases. The investigated results in this paper are of significance for understanding the solid-liquid interaction mechanism in debris flows as well as disaster prevention and mitigation engineering. © 2023 Academia Sinica. All rights reserved.