Observations and Interpretation from a Centrifuge Test on a Pile-Supported Wharf Subjected to Combined Superstructure Inertia and Lateral Ground Deformations

Seismic vulnerability studies of port facilities often involve evaluating the seismic response of pile foundations subjected to lateral ground deformations caused by liquefaction and/or cyclic softening of native soils adjacent to the piles. However, there is a knowledge gap and lack of consensus in design standards and guidelines regarding the combination of structural inertial loads and kinematic lateral ground deformation in pseudo-static analysis. This knowledge gap becomes even wider for piles embedded in low-plasticity silts, commonly prevalent in port environments, as the rate of cyclic shear strain accumulation in these transitional silts differs from the behavior observed in liquefiable sands. This paper presents the results of a large-scale centrifuge test on a pile-supported wharf structure. The wharf deck was supported by 21 piles representing 0.76-m diameter concrete piles at prototype scale. The piles were embedded in a sloped rockfill overlying low-plasticity silts and dense sand. The model was subjected to short- and long-duration earthquake motions, which induced permanent lateral slope deformations up to 0.3 m in prototype scale due to the generation of excess pore pressures and associated deformations in the underlying silt and the inertial loading of the slope. Based on the experimental results, it was found that peak, or close to peak, kinematic demands coincided with 56% to 68% of the peak superstructure inertial demands. These results provide a range of load factors that could be considered in pseudo-static analysis of pile-supported structures in liquefiable soils and sloping ground conditions.