A series of effective stress analysis were performed on a caisson type quay wall in Kobe Port during 1995 Hyogo-ken Nanbu earthquake. The caisson wall with a water depth of 14m was located at south coast of Rokko Island, exhibited seaward displacements of 4 to 5m, settlements of about 2m, and seaward tilting of about 4 degrees. The effective stress model used for the analysis was a strain space multiple mechanism model, which takes into account the effect of rotation of principal stress axis during cyclic loading. The model parameters were determined by referring to various investigations including in-situ freezing sampling, cyclic triaxial tests and velocity logging.
　The analysis resulted in seaward displacement of 3.5m, settlement of 1.5m, and seaward tilting of about 4 degrees, being consistent with the deformation induced during the earthquake. A parametric study indicated that about half of these deformations are due to pore water pressure increase in the soils beneath and behind the caisson wall and the rest are dur purely to the inertia force. Though the vertical input motion was very large, its effect was minor because vertical response of the caisson was mainly induced by rocking dur to horizontal input motion.