Seismic performance of block-type quay walls with liquefiable calcareous sand backfill

Abstract

Block-type gravity quay walls are widely used in remote oceanic regions due to their cost and construction efficiency, where backfill and foundation soil often consist of liquefiable calcareous coral sand. The lack of connection between blocks and hence structure integrity can result in poor seismic performance of block-type quay walls, especially in liquefiable soil. Based on laboratory element tests on calcareous sand, centrifuge shaking table test, and high-fidelity numerical simulation, this paper investigates the seismic performance of block-type quay walls with liquefiable calcareous sand backfill. Undrained cyclic torsional shear tests are conducted on South China Sea calcareous coral sand to determine its dynamic properties, which are used to calibrate the unified plasticity model for large post-liquefaction shear deformation of sand. A centrifuge shaking table test is conducted to obtain the basic physical seismic response of a block-type quay wall in liquefiable calcareous backfill sand. Utilizing the understanding from laboratory tests, fully coupled dynamic effective stress analysis using the calibrated constitutive model is conducted. The influence of seismic input, quay wall structure, and backfill sand properties on the seismic response of the quay wall is analyzed. Input motion intensity and frequency are shown to be influential to the seismic response of the quay wall. Increase of backfill soil density, permeability, and block to block connection can significantly improve the seismic performance of the quay wall.