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Experimental Study on Earthquake Resistance of Underwater Granular Structures

水下粒状结构抗震试验研究

基本信息

批准号：
02805052
负责人：
KONAGAI Kazuo
金额：
$ 1.22万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

A new experimental technique to visualize the dynamic behavior of underwater particle assemblage (LAT: Laser-Aided Tomography) was developed. According to the proposed method, a granular structure model, made of particles of crushed glass and immersed in liquid with the same refractive index, consequently becomes invisible. An intense laser-light "sheet" (LLS) is then passed through it, illuminating the contour lines of all the particles within a cross-section. Scanning the model with LLS allows a 3D image of every discrete particle's shape and motion to be obtained as well as the whole-field deformation of the model. Utilization of this method with a smaller particle size will expand its application to analyses of structures made up of finer grains. In this case, however, it is not easy to have a clear look at each particle on the LLS. Some techniques were developed to overcome the problem, and we could reduce the grain size of the employed glass material to lmm or smaller.Dynamic failure test of embankment-shaped models were conducted using the proposed technique. The models made of screened particles ( 2mm < grain < 5mm ) were shaken sinusoidally in the liquid. The surface of the model began to slide when the amplitude of base acceleration exceeded a threshold. The threshold acceleration increased with excitement frequency, while variation of threshold velocity was rather small, and was scattered in the range of 0.5 to 2.0 kine.The failure process and its frequency dependence observed in LAT experiments was then discussed using the Discrete Elliptic Element Method (DEEM), considering contributions of overall slip and roll to the failure process. The DEEM simulation gave us a general idea of the dilatation effect on overall behavior and its frequency dependence.

发展了一种新的水下颗粒群动态可视化实验技术（LAT：Laser-Aided Tomography）。根据所提出的方法，颗粒状结构模型，由破碎的玻璃颗粒制成，并浸入具有相同折射率的液体中，因此变得不可见。然后，一个强激光“片”（LLS）通过它，照亮横截面内所有颗粒的轮廓线。使用LLS扫描模型可以获得每个离散颗粒的形状和运动的3D图像以及模型的全场变形。利用这种方法，在更小的颗粒尺寸将扩大其应用于分析由更细的晶粒组成的结构。然而，在这种情况下，要清楚地看到LLS上的每个粒子并不容易。为了克服这一问题，我们开发了一些技术，可以将所用玻璃材料的晶粒尺寸减小到1 mm或更小。将筛过的颗粒（2 mm <5 mm）制成的模型在液体中正弦振荡。当基底加速度的幅值超过某一阈值时，模型表面开始滑动。临界加速度随激励频率的增加而增加，而临界速度的变化很小，且分散在0.5 ~ 2.0kine之间.利用离散椭圆单元法（DEEM）分析了LAT实验中观察到的破坏过程及其频率依赖性，考虑了整体滑移和横滚对破坏过程的贡献. DEEM模拟为我们提供了膨胀效应对整体行为及其频率依赖性的一般概念。