The Role of Liquefaction on the Seismic Response of Quay Walls during the 2014 Cephalonia, Greece, Earthquakes

Following the Cephalonia, Greece, 2014 earthquake sequence (M-w = 6.1 and M-w = 6.0), liquefaction of gravelly earthfill materials at the ports of Lixouri and Argostoli resulted in the manifestation of ground cracking and coarse-grained soil ejecta, and the quay walls in these ports exhibited lateral ground displacements ranging from 0.1 to 1.5 m. To evaluate the seismic performance of the port quay walls, numerical analyses using the finite-difference method were performed, and the results compared with the observed response. Three commonly used constitutive models (PM4Sand, UBCSand, and URS/ROTH) calibrated based on in situ site investigation data were considered in modeling the liquefiable earthfills. The results of the numerical analyses at both ports using the best-estimate parameters indicate that taller walls exhibit smaller lateral ground displacements than shorter walls, something that is in line with field observations. For the shorter walls, liquefaction-induced lateral spreading played an important role in the observed response, whereas for the taller walls, the seismic behavior is dominated predominantly by the dynamic response of the structural system. PM4Sand and UBCSand models seem to yield very similar deformational results, but the URS/ROTH model, which assigns residual shear strength parameters once liquefaction is triggered, resulted in horizontal displacements that are closer to the observations for short-wall geometries but overpredict the response when the effect of liquefaction on the overall displacements is small. Finally, the numerical analyses demonstrate the strong influence of the pulselike characteristics, as well as the polarization of the input motion on the seismic response of the Lixouri quay walls, indicating that forward directivity contributed significantly to the observed quay wall deformations. (c) 2021 American Society of Civil Engineers.