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

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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.