Seismic response of offshore composite caisson-piles foundation with different pile configurations and soil conditions in centrifuge tests

A series of centrifuge shaking table tests were performed on a new type of foundation, the composite caisson-piles foundation (CCPF) which is recently suggested for the cross-sea bridge or offshore engineering, to investigate its seismic response. The CCPF model with 2 x 2 and 3 x 3 pile groups embedded in homogeneous clayey silt or layered soil consisting of dry sand underlain by clayey silt were employed, these being representative of different pile configurations and soil conditions respectively, with the superstructure simplified as lumped mass and connecting column. The horizontal acceleration and lateral displacement of the soil and superstructure, as well as bending moment of piles were recorded during seismic shaking. Due to the complex soil-CCPF-structure interaction, the composite caisson-piles foundation with the two type pile groups in homogeneous or layered soil exhibited quite different behaviors under earthquake loading. These centrifuge test results indicated that both soil condition and pile configuration played an important role in the seismic response of the CCPF, and future studies combining experimental and numerical simulation should be conducted to investigate more factors influencing the seismic behavior of the composite caisson-piles foundation.