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

这项研究是我们在1989年至1990年进行的同一题目下的研究的继续。在先前的研究中，我们开发了一个动态激励系统在转鼓离心机。该系统被设计用于观察长结构（如桩线）的行为。本研究是动态激振系统的一个应用，现场观测表明，地震引起的管道破坏集中在两种不同土壤类型的沿着边界区域或液化区域。在前一个区域的损害已在以前的研究中进行了深入的研究。因此，本研究的重点是在转鼓离心机的液化现象的建模系统的发展。本研究取得了以下成果：1）设计并制作了一种具有多层框架结构的矩形容器。容器直接固定在先前研究中开发的动态激励系统上。具有饱和砂体的容器的质量为2.5kg。在离心加速度为40.2时，砂层高度相当于原型比例尺中的3m。为了检验离心场下动力行为中的时间相似律，使用了两种类型的孔隙流体液体。它们是水和硅油，硅油的粘度比水大30倍。通过一系列不同加速度下的试验，发现相对密度为40%的砂土存款在大于100 gal的水平加速度下完全液化。这一观察结果与从现场数据得出的结论一致。4）现在可以设想，利用这种开发的系统，很有可能进行模型试验，以研究通过液化层的长结构的行为。

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.