Liquefaction Effects on Piled Bridge Abutments: Centrifuge Tests and Numerical Analyses

Earthquake-induced deformation of piled bridge abutments in approach embankments underlain by liquefied soils may be reduced by the restraining forces provided by the piles and bridge superstructure. Design methods accounting for these pinning effects have been applied in practice but lack significant comparison with actual physical data. Three dynamic centrifuge model tests were performed to investigate pile-pinning effects, and the results are presented in this paper. Each centrifuge model was composed of two identical embankments underlain by liquefiable soil: one with a pile group and the other without. The tests demonstrated that the embankment with a pile group experienced less lateral movement and settlement than the embankment without a pile group. To better understand and extend the results of these centrifuge tests, nonlinear deformation analyses of the three centrifuge tests were made using a fully coupled effective stress model. The ability of the analyses to model the centrifuge tests is assessed primarily through comparison of dynamic histories of acceleration, pore water pressure, displacement, and pile bending moments. The usefulness of the modeling and dynamic analysis procedures is evaluated, and key lessons are described.