Experimental study on seismic response of gravity-type quay wall considering input earthquake frequency and excess pore pressure buildup in backfill

In performance-based seismic design of port structures, it is crucial to accurately verify the seismic performance of structures. Therefore, there is an increasing demand for investigation of the seismic behavior of quay walls, considering the comprehensive interaction between the backfill, quay wall, and water. In this study, to evaluate the influence of the earthquake frequency and excess pore pressure buildup in the soil on the seismic responses of a gravity-type quay wall, a dynamic centrifuge test was performed. Four earthquake motions were applied to a quay wall model under saturated soil conditions. The measured records of acceleration responses and pore pressure in the soil and wall displacement showed that the earthquake frequency is strongly associated with permanent displacement of the wall and liquefaction in the soil. Based on time–frequency analysis, the frequency band of the input motion, which mainly contributed to the generation of permanent displacement of the wall, was found. Contrary to the hypotheses of conventional simplified analysis methods, the phase relationship between measured dynamic displacements of the wall and soil, excess pore pressures, and dynamic thrust showed that excess pore pressure buildup in backfill is a crucial factor in determining the dynamic thrust acting on the quay wall.