基于两层两相光滑粒子流体动力学法的饱和土柱垮塌模拟研究

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

在泥石流、雪崩等自然灾害中,固–液两相流普遍存在。针对固–液两相之间复杂的相互作用机制和现有数值计算方法的不足,通过结合土体本构方程,建立两层两相光滑粒子流体动力学(SPH)数值模拟方法,在连续介质理论框架下运用统一的控制方程实现水土两相耦合模拟。通过空气中饱和土体垮塌数值算例近似真实的泥石流事件,借此验证所建立的数值方法在计算流体、土体以及土水耦合相互作用问题时的精度及可靠性,在此基础上,对流体黏度、土体有效粒径和初始孔隙率等参数进行敏感分析,并对比土–水耦合中不同的渗流模型的影响。结果表明:两层两相光滑粒子流体动力学法用于模拟土水耦合大变形问题是合理有效的;环境流体及土体的参数对结果有重要影响;粒子雷诺数较大时,渗流模型对于正确模拟固–液两相之间的相互作用和捕捉固相和液相之间的界面至关重要。该工作对于充分理解泥石流中的固–液相互作用机制及防灾减灾工程具有一定的参考意义。

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 soilwater 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.