Study on the Behavior of Long-Structures Modeled in a Drum Centrifuge

这项研究是我们在1989至1990年间进行的同名研究的延续。在以前的研究中，我们在转鼓离心机中开发了一种动态励磁系统。该系统是专门为观察长结构(如桩线)的行为而设计的。这项研究是动态激励系统的应用。现场观测表明，地震对管道的破坏集中在两种不同土类的边界或液化区域。前一地区的破坏在以前的研究中已经被深入研究。因此，本研究的重点是开发转鼓离心机液化现象的模拟系统。1)设计并制造了一种具有一系列层状框架的矩形容器。容器被直接固定在先前研究开发的动态励磁系统上。容器的质量为2.5公斤，容器主体为饱和沙子。在离心力为40.2的情况下，砂层的高度在原型尺度上相当于3米)为了检验离心场下动态行为的时间相似规律，使用了两种孔隙流体液体。它们是水和硅油，它们的粘度是水的30倍。3)通过一系列不同加速度的试验，发现相对密度为40%的堆积砂在100ga以上的水平加速度作用下完全液化。这一观察结果与现场数据得出的结论是一致的。4)根据目前的设想，利用这个发展起来的系统，很有可能进行模型试验来研究长结构在液化层上的行为。

This study is a continuation of our study under the same title conducted from 1989 to 1990. In the previous study we developed a dynamic excitation system in a drum centrifuge. The system had been designed with special purposes for observation of the behavior of long-structures such as pile lines. This study is an application of the dynamic excitation system.Field observation has revealed that damage of pipelines due to earthquake concentrates in regions of either along boundaries of two different soil types, or liquefied. The damage in the former region had been intensively studied in the previous study. This study thus focused on the development of a modeling system for liquefaction phenomena in the drum centrifuge. The following results were obtained from this particular study.1) A rectangular container with a series of laminar frame was designed and made. The container was directly fixed on the dynamic excitation system developed in the previous study. The mass of the container with a body of saturated sand was 2.5kg. The height of the sand layer corresponds to 3 meter in a prototype scale at the centrifugal acceleration of 40.2) In order to examine the similarity law of time in a dynamic behavior under a centrifugal field, two types of liquid for pore fluid were used. They were water and silicon oil, of which viscosity is 30 times larger than that of water. It was confirmed that the scaling law in terms of time is of essence for the study of dynamic behavior, and the correct modeling of viscosity is important.3) It was observed from a series of tests with deferent accelerations that a sand deposit with the relative density of 40% was fully liquefied under the horizontal acceleration of more than 100 gal. This observation is consistent with the conclusion drawn from field data.4) It is now envisaged with this developed system that it is highly possible to carry out model tests for the study of behavior of a long structure passing on a liquefied layer.