The dynamic behavior of the gravity type quay walls during the earthquake was investigated experimentally and analytically, and the effect of the liquefaction of the backfill ground on the dynamic earth pressure and the damage to the quay wall was made clear. Series of model shaking table tests under gravitational and centrifugal forces were conducted, focusing on the occurrence of the liquefaction in the backfill ground. The fluctuating earth pressure on the caisson is quite different in magnitude and phase angle difference with inertial force, whether liquefaction of backfill occurs or not. The careful examination of fluctuating earth pressure in the process of liquefaction showed that the interaction between caisson and backfill controls the fluctuating earth pressure; the fluctuating earth pressure changes as a function of natural frequency of backfill with respect to that of the caisson, which reduced due to the softening of backfill induced by the liquefaction. This feature is demonstrated by the simplified mass-spring-dashpot model proposed by the authors. Also the dynamic behavior of gravity type quay wall is simulated by using non-linear Finite Element Method (FLIP).
Significant damages were caused by liquefaction in the reclaimed lands of port and harbor facilities during the recent earthquakes in Japan. The functions of quay walls were frequently lost severely when the gravity type quay wall caissons were displaced toward sea and/or subsided due to the thrust from the liquefied backfill ground. The authors have investigated the mechanism of the damage to gravity type quay walls during earthquake focussing on the liquefaction of the backfill ground (see Miura, et. al.; 1997). From a series of shaking table tests conducted on the model quay walls with dense and loose backfills conducted by Miura et al. (1997), it was found that the relationship between inertial force and earth pressure on the caisson determines the damage to the quay walls.