OBSERVATION OF THE SEISMIC BEHAVIOR OF GRAVITY TYPE QUAY WALL AND DEVELOPMENT OF ITS EARTHQUAKE RESISTANT DESIGN.

本研究项目旨在解释地震引起码头墙失稳的机理，阐明液化对沉箱与回填地基相互作用的重要影响。对日本包括1995年小古根南部地震在内的几次强震造成的重力型码头墙破坏的密切调查表明，破坏程度与回填地基液化的发生密切相关。与未经处理的码头墙经常出现的严重破坏形成鲜明对比的是，经过处理的防液化码头墙可以在强烈地震中存活下来，几乎没有损坏。在此基础上，重点研究了填土液化对模型码头壁面的影响，进行了一系列模型振动台试验。研究发现，随回填地是否发生液化，沉箱的运动有很大的不同。当沉箱不发生液化时，沉箱受到较大的压力抑制了沉箱的运动。另一方面，当回填地基发生液化时，由于土压力波动分量与惯性力在相位角上重合，沉箱的滑动增强。在模型振动试验中，还仔细观察了液化过程中作用于沉箱后壁的脉动土压力。这表明沉箱的稳定性准则不应根据液化的开始而应根据突然的相变来制定。在日本北海道钏路港进行了全尺寸试验重力式岸墙在地震作用下的动力特性现场观测，旨在确认液化对岸墙破坏的决定性作用，为挡土墙地震土压力评估和制定合理的重力式岸墙抗震设计方法提供信息。在2003年的枥树地震中，试验码头墙受到V+级地震的震动。通过对试验岸壁实测动力特性的分析，揭示了液化对试验岸壁变形的影响。少

This research project was conducted aiming to explain the mechanism of the instability of quay wall induced by earthquake, and clarify the significant influence of liquefaction on the interaction between the caisson and the backfill ground. The close investigation of the damage to gravity type of quay walls caused in several strong earthquakes in Japan including the 1995 Hyogoken-nambu Earthquake, clarified that the degree of damage was strongly related to the occurrence of liquefaction in the backfill ground. The treated quay walls against liquefaction could survive the strong earthquakes with little or no damage, in marked contrast to the severe damage frequently seen in untreated quay walls.Then, we conducted some series of model shaking table tests on model quay walls focusing on the effect of liquefaction in the backfill ground. The movement of the caisson was found to be quite different depending on whether liquefaction occurred in the backfill ground or not. The fluctuating eart … More h pressure on the caisson suppressed the movement of the caisson when liquefaction did not occur. On the other hand, sliding of the caisson was enhanced since the fluctuating component of earth pressure and the inertial force coincide in phase angle, when liquefaction occurred in the backfill ground. The fluctuating earth pressure acting on the back wall of the caisson in the process to liquefaction was also carefully observed in the model shaking tests. This suggested that stability criteria of the caisson should be developed not by the onset of the liquefaction but by the sudden phase change.We also conducted a field observation of dynamic behavior of full-scaled test gravity type of quay wall during earthquakes in the Port of Kushiro, Hokkaido, Japan, aiming to confirm the decisive effect of the liquefaction on the damage to quay wall, and provide information for the evaluation of seismic earth pressure on retaining structure and the development of rational earthquake resistant design method for gravity type quay wall. In the 2003 Tokachi-oki Earthquake, the test quay wall was shook with the seismic intensity of rank V+. The analysis of the observed dynamic behavior the test quay wall showed the effect of the liquefaction on the deformation of the test quay wall. Less