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基于散体介质理论的三维离散元数值分析方法,引入粘滞阻尼模型考虑系统耗能效应,求解固体作用力和流体连续性方程,充分考虑流固耦合作用,对中、细标准砂泥石流过程进行仿真分析,得到不同砂型泥石流破坏过程及渗流场、颗粒速度场、孔隙率、颗粒接触数等参数变化规律。分析表明,中砂、细砂分别表现出分层渐进式和流滑型的破坏模式,这与已有物理试验现象吻合,验证该模型的适用性,并从渗流场分布规律深刻解释该现象发生机理。泥石流过程中土颗粒速度矢量变化规律从细观上揭示了隐藏在颗粒内部的相互碰撞、摩擦、滑动等复杂运动特点,从宏观上揭示了中砂土坡脚薄弱位置率先突破,主滑动体形成直至完全失稳的分级渐进式破坏过程。进一步分析了土体孔隙率和平均接触数分布云图变化规律,中砂泥石流过程中随颗粒运动,滑动体孔隙率逐渐增大,颗粒接触数逐渐减小,并且这种发展趋势逐渐往坡后方土体蔓延;进一步揭示了中砂泥石流分级渐进破坏过程与颗粒速度场分析规律一致。分析结果表明了该模型方法在模拟泥石流这种大变形、流固耦合问题上的适用性,这对泥石流复杂机理的更深入探索是有益的。
Based on the three-dimensional discrete element method for numerical analysis of granular media, the viscous damping model is introduced to consider the energy dissipation effect of the system. The solid force and fluid continuity equation are solved. The fluid-solid interaction is fully taken into account. Through the simulation analysis, the damage process of different sand debris flows and the change rules of seepage field, particle velocity field, porosity and particle contact number are obtained. The analysis shows that the medium sand and fine sand show the failure modes of layered progressive and slippery, respectively. This is in good agreement with the existing physical experiments to validate the applicability of the model and explain the phenomenon deeply from the distribution law of seepage field mechanism. In the process of debris flow, the variation law of the velocity vector of the soil particles reveals the complex kinematics of mutual collision, friction and sliding concealed inside the particles from the microscopic view. From the macroscopic view, we can see that the weak position of the soil slope first breaks through and the main sliding body forms Until completely destabilized graded progressive destruction process. Further analysis of the distribution of soil porosity and the average number of contacts cloud pattern changes, sand debris flow in the process with the particle movement, the porosity of the sliding body gradually increases, the particle contact number decreases gradually, and this trend gradually toward the slope of the rear soil Body spread; further revealed that graded sand debris flow progressive destruction process consistent with the particle velocity field analysis. The analysis results show the applicability of the proposed model method in simulating the large deformation and fluid-structure interaction problems of debris flow, which is beneficial to the further exploration of the complicated mechanism of debris flow.