Abstract: Dynamic centrifuge tests are carried out to study seismic response of caisson-pile composite foundation. With Shanghai sandy silt chosen as test soil, laminar shearing box used to eliminate reflection at the boundary, and Shanghai artificial middle wave is taken as the input motion, three tests with different foundation types are conducted under the centrifuge acceleration of 50g. Single pile, caisson and caisson-pile composite foundation are the foundation types for those three tests, and all the superstructures in these tests are simplified as mass points and connecting columns. Test results indicate that, for soil with low stiffness acceleration decays in the process of earthquake wave propagating upwards; adding piles under the caisson could decrease the earthquake responses of both the foundation and structure, so the reinforcement of the system in resisting earthquakes is expected; frequency characteristics of the responses at soil surface, foundation and structure are all different from each other depending on their own natural vibration characteristics; and for the interaction between soil and foundation, or foundation and structure, only the earthquake component with similar frequency with both interacting sides can cause remarkable earthquake interaction.

Key words: caisson-pile composite foundation, centrifuge test, earthquake, interaction, frequency characteristic