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Physical elucidation of the behaviors of sand-pile avalanches like self-organized criticality and like characteristic earthquakes

对沙堆雪崩行为（如自组织临界性和特征地震）的物理解释

基本信息

批准号：
18340134
负责人：
YOSHIOKA Naoto
金额：
$ 6.96万
依托单位：
Yokohama City University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

It is known that the behavior of avalanches in sandpile experiments is categorized into two types; one is the self-organized criticality like behavior, and another is the characteristic earthquake like behavior. These two types are determined solely by the ratio of sand diameter to the diameter of the disk on which the sandpile is created. This fact has been confirmed by a number of experiments, but the satisfactory physical explanation has not been given. The purpose of this study is to clarify the underlying physics of this phenomenon. We focus on the stress chain structure inside a sandpile. So we use a photo-elastic analysis of two-dimensional sandpile made of photo-elastic material and a simulation by discrete element method(DEM).A detailed observation of the results of the experiment and the simulation suggests a possible mechanism of avalanches: for a sandpile in a critical state, what determines the size of avalanches may be some kind of inhomogeneity.When the pile is small, the size of avalanches is small because the uneven distribution of particles on the surface may be the dominant inhomogeneity of the system. When the pile becomes large, however, the deep inside of the pile is tightened and consolidated while the part near the surface is never tightened because of the repeated avalanches. The contrast in strength becomes the main factor of the inhomogeneity.

沙堆实验中的雪崩行为可分为两类：一类是自组织临界行为，另一类是典型的地震行为。这两种类型仅由砂直径与沙堆所在圆盘直径的比值决定。这一事实已被许多实验所证实，但尚未给出令人满意的物理解释。这项研究的目的是澄清这种现象的基本物理学。我们专注于沙堆内部的应力链结构。为此，本文对光弹材料制成的二维沙堆进行了光弹分析，并利用离散元法（DEM）进行了模拟。通过对实验结果和模拟结果的详细观察，提出了雪崩的可能机制：对于处于临界状态的沙堆，决定雪崩大小的可能是某种不均匀性。2当沙堆很小时，雪崩的大小很小，因为表面上颗粒的不均匀分布可能是系统的主要不均匀性。然而，当桩变大时，桩的内部深处被拉紧和加固，而靠近表面的部分由于反复的雪崩而从未被拉紧。强度的差异成为影响非均匀性的主要因素。