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Micromechanical Approach to Flow-Initiation Mechanism in Debris Flows.

泥石流中流动引发机制的微机械方法。

基本信息

批准号：
03650413
负责人：
KISHINO Yuji
金额：
$ 1.09万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03650413/
关键词：
Micromechanics Debris Flow Flowing Mechanism Simulation Granular Element Method Pore Pressure Two Phase Behavior Eigen-Value Analysis シミュレ-ション

项目摘要

The debris flow is a mechanical phenomenon which is very hard to analyze, because it exhibits the solid-like behavior as well as the fluid-like behavior. In this research project, an investigation with GEM (granular element method) was attempted as a micromechanical approach to the debris flows. The main characteristic of GEM is that it utilizes the stiffness matrix unlike other distinct element methods. Although this research has not yet reached the quantitative evaluation of real phenomena, it presents a contemplative model to clarify the complicated mechanism of debris flows.The first part of this research is the presentation of eigenvalue analysis for granular assemblies. The eigenvalue analysis, which is usually applied to the strain-localization analysis in solid continua, was developed so as to be able to handle discrete media. A new idea called the eigen-mode expansion was also presented. A simple example applied for a shearing test of granular model shows the effectiveness of this approach.The second part of this research is directed to the modeling of pore-water pressure which is inevitable in analyses of debris flows. A stability analysis of granular slope with pore water gives an important hint for the flow-initiation mechanism of debris flows. Considerations through the calculation of coordination tensor and the eigenvalue analysis were also presented. From observation of the results obtained by the eigenvalue analysis, it was found that the flow-initiation mechanism which reflects fluid-like behavior of debris flow is quite different from the strain-localization mechanism in granular assemblies.The last part of this research is the presentation of a new simulation model to analyze the transitional phenomena of granular assemblies which behave as solids and as fluids. The method will be called Dynamical Granular Element Method. The application to a dynamical behavior of granular slope demonstrates the effectiveness of this new method.

泥石流是一种很难分析的力学现象，因为它既表现为类固体行为，也表现为类流体行为。在本研究项目中，尝试将颗粒单元法(GEM)作为泥石流的细观力学方法进行研究。与其他离散单元方法不同，GEM的主要特点是利用了单元的刚度矩阵。虽然这项研究还没有达到对真实现象的定量评估，但它为阐明泥石流的复杂机制提供了一个沉思模型。本研究的第一部分是颗粒集合体的特征值分析。为了能够处理离散介质，发展了通常用于固体连续介质应变局部化分析的特征值分析方法。提出了本征模展开的新概念。通过一个简单的颗粒模型剪切试验的算例，说明了该方法的有效性。本研究的第二部分针对泥石流分析中不可避免的孔压建模问题。含孔隙水的散体边坡稳定性分析为泥石流的发流机理提供了重要的线索。文中还提出了通过计算配位张量和进行特征值分析的考虑。通过对特征值分析结果的观察，发现反映泥石流类流体行为的起流机制与颗粒集合体的应变局部化机制有很大的不同。这种方法将被称为动力颗粒单元法。将该方法应用于散体边坡的动力行为，验证了该方法的有效性。