Lateral spreading of ports in the 2014 Cephalonia, Greece, earthquakes

摘要

A case history is presented of lateral spreading in two reclaimed port areas of the Cephalonia island, Greece, in the 2014 earthquake doublet (M-w 6.1 & 6). Lateral ground displacements along 24 transects perpendicular to the quay walls in the two port areas were directly measured by ground surveys. Liquefaction of gravel-size fills was observed throughout the ports and was more pronounced in Lixouri port where ground motions were higher. The maximum cumulative horizontal ground displacements ranged from 3 cm to 152 cm, depending on the transect location and height of free face, whereas the inland extent of lateral ground movement ranged from 10 m to 90 m. Lateral movement of the quay walls in Argostoli Port was lower compared to Lixouri Port. Strong motion recordings in the two port areas as well as pertinent seismotectonic data are also presented along with the available geotechnical data compiled by integrating information from exploratory borings, trial pits, site geology and eye-witness accounts of the reclamation history of the areas. Average cumulative lateral displacements for groups of transects, characterized by similar height of quay wall and field conditions were derived and compared to lateral spreading predictions using an empirical relationship for free field conditions. It was found that the magnitude of lateral spreading behind the gravity-type quay walls was significantly lower compared to empirical predictions based on the assumption of free field conditions. The reduction of lateral ground movement depends on the height of quay wall and may even be an order of magnitude lower for wall heights of 6 m or greater. The findings of this study contribute in assessing quay wall movement in port areas especially when liquefaction has occurred behind the wall.