In order to study the effects of liquefaction on quay walls during earthquakes, effective stress analyses are conducted on the field performance of two quay walls during an earthquake. The quay walls are of anchored steel sheet piles. Though the cross sections were similar to each other and the locations were adjacent to each other, one quay wall suffered serious damage while the other did not.
　The effective stress model used in the analysis consists of a multiple shear mechanism defined in strain space. The model has the capability to represent essential features in the cyclic behavior of sand such as the effects of rotation of principal stress axis directions. For estimating the model parameters, soils were taken from the site for laboratory tests. The record of the earthquake motion was recovered from the site and digitized for the analysis.
　Results of the effective stress analyses are basically consistent with the observed performance of the quay walls; the model demonstrated the potential ability to differentiate between serious large deformations (i.e.damage) from negligibly small deformations(i.e. no damage) in similar types of sheet pile quay walls.