Keywords: quay wall, liquefaction, earthquake, effective stress, constitutive model.

In the period from 1964 to 2003 a number of well-documented case histories of damage to port structures made of gravity retaining quay walls show that the damage is often associated with significant deformation of liquefiable soil deposits. Gravity quay wall failures have stimulated great progress in the development of a deformation-based design method for geotechnical structures.

A two-dimensional effective stress method of analysis based on the generalised elasto-plasiticity constitutive model of Pastor, et al. [1] with slight modifications incorporated into a new FEM procedure. The FEM method is evaluated by back analysing the typical Port Island PC-1 caisson type quay wall which was damaged by the 1995 Hyogoken-Nanbu earthquake.

The model was first validated by simulating published cyclic test results. The results of the monotonic testing showed excellent agreement between the physical and numerical experiments. For the cyclic tests, the simulations were able to capture the general behaviour exhibited in the physical experiments, in that, the stress and strain histories of the numerical simulations showed comparable shapes to the physical experiments.

A model of Port Island quay walls was then developed using the finite element package UWLC. Both vertical and horizontal accelerations were applied to the model and the results compared to the observed field measurements. The computed overall displacement and rotations of the wall were similar to those observed in the field, obtained from the Ministry of Transport, Japan [2], consisting of seaward displacement, settlement and tilting which are known to characterise typical failure modes of quay walls due to earthquakes.

Three different values of permeabilities were analysed to investigate the influence of permeability on the development of pore pressure behind the wall, the results show that when permeability increases the accumulation of pore pressure is reduced. Furthermore if the permeability is low enough the pore water pressure will not readily dissipate.

Finally, it is concluded that effective stress analysis is a powerful tool that can describe the seismic response of port structures including liquefaction failure modes.

1

Pastor M., Zienkiewicz O.C., Chan A.H.C., "Generalized Plasticity and the modelling of soil behaviour", Int. J. Numerical and Analytical Methods in Geomechanics, 14, 151-190, 1990. doi:10.1002/nag.1610140302

2

Japanese Ministry of Transport, "Damage to port and port-related facilities by the 1995 Hyogoken-nanbu Earthquake", The Port and Harbour Research Institute, Japan, 777-792, 1997.

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