Man-made islands have recently been considered as possible new construction sites for a variety of facilities. The performance of the seawalls bounding these islands when subjected to seismic loading is an important aspect of design. To obtain data on the performance of such structures when founded on a medium dense sand seabed and supported by an armored embankment, a series of large scale centrifuge models were tested at the University of California, Davis. The concrete caisson within the seawall was found to settle, displace laterally and rotate slightly away from the backfill. However, the deformations were limited, and global failure of the structure did not occur despite base accelerations of up to 0.6 g. The model accelerations were amplified up through the substratum and caisson during relatively small events, but were strongly attenuated during the larger events. Zones containing high excess pore pressures were generally located towards the top of the sand fill forming the island, and in the seabed below the toe of the armored embankment. These zones grew progressively larger as the event magnitude increased, and accordingly the times for pore pressure dissipation to occur lengthened with increasing event magnitude.
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