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

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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