Seismic effective stress analysis of quay wall in liquefiable soil: The case history of Kobe

Abstract

During the previous decades, a significant number of failures of caisson quay walls have been observed. In particular, the majority of these failures are strongly connected to the deformational response of the surrounding (i.e. the backfill and the foundation) soil deposits subject to liquefaction. In this paper, the seismic effective stress analysis method is applied in order to investigate this complex phenomenon, through the use of the UBC3D-PLM constitutive model for stress-strain soil behaviour, which is available in the material library of the PLAXIS finite element code. An optimization procedure is presented for calibrating the parameters of the aforementioned constitutive model, which involves a two-step methodology based on matching: (a) the response of a single soil element under undrained monotonic direct simple shear loading reproduced by a recently developed more sophisticated model for sand, and (b) the cyclic resistance ratio curve in accordance with the NCEER/NSF procedure. The capability of the model in describing the response of a gravity-type quay wall undergoing lateral spreading due to soil liquefaction is then validated against a well-documented case history from the 1995 Kobe earthquake. The latter analysis is shown to reproduce satisfactory engineering accuracy in comparison to the observed response, shedding light to the validity of the proposed calibration methodology.