高速远程泥石流中的颗粒分选机理及其对流动性影响的研究

Debris flow occurs as masses of poorly sorted sediment agitated and saturated with water surge down due to gravity. As a special two-phase flow (solids and slurry), debris flows in nature usually behave like most liquids and have rheological properties. In this project, the principles of granular flows and solid-water two-phase flows are applied for the research of the dynamics of long run-out debris flows in nature. Field investigation, flume model testing, and numerical study through CFD coupled Discrete Element Method (DEM) will be conducted. The mechanisms of solids segregation and its effect on the debris-flow mobility will be systematically investigated. Based on this research work, the widely applied two-phase flow model (e.g., Iverson model) for debris flows will be modified and a new numerical tool to simulate natural debris flows will be developed. It hopes that this study can improve the research on the mechanisms of debris flows and be helpful for the risk prediction and hazards mitigation in future.

泥石流是固体颗粒物质和水充分掺混的一种地表过程，其整体运动呈流体状，具有明显的流变特性，是一种特殊的固液两相流。本项目从颗粒流和固液两相流动力学的角度出发，研究我国常见的高速远程泥石流的颗粒分选和流动性激增现象。在野外原型调研的基础上，通过理论分析、水槽实验、流固耦合的数值模拟实验相结合的方法，研究泥石流中颗粒分选对流动性的影响，重点描述泥石流固液相间作用机制和固体颗粒的分选机理，并揭示泥石流体内部剪切速率对床面（基底）摩阻力的影响，完善对泥石流运动中的物质交换和能量损耗的认识；进而改进现有的泥石流运动两相流模型，提高研判泥石流危害范围的准确程度，为规避泥石流运动路径、降低泥石流的危害提供科学依据和技术支撑。

泥石流是一种特殊的固液两相流。本项目从颗粒流和固液两相流动力学的角度出发，研究高速远程泥石流的颗粒分选和流动性激增现象，提高研判泥石流危害范围的准确程度，为规避泥石流运动路径、降低泥石流的危害提供科学依据和技术支撑。本研究通过野外考察，采样了真实泥石流的样本，获取了泥石流的土力学参数及分选相关特性指标。在此基础上，开展了泥石流分选物理模型实验和流固耦合的数值模拟实验，探索了泥石流不同流态、颗粒级配、含水率、孔隙间流体粘滞度等对颗粒分选的影响，确定了泥石流分选的临界含水率，揭示了泥石流分选的机理，即流体拖曳力是影响泥石流剪切速率发展进而延缓颗粒分选的关键因素。在此基础上，研究还提出一个考虑分选效应的泥石流综合摩阻力计算模型，研发了多相流新模型。通过对比数值模拟和物理模拟实验的结果，并推演真实泥石流事件的全过程，验证了多相流模型的正确性，从而为定量的灾害风险分析奠定了坚实的理论基础。项目成果将有效的指导规避灾害的潜在危害、保障安全等方面发挥重要的作用。