Pile–Soil Interaction Effect on High-Speed Railway Track–Bridge System Under Earthquake

The foundation of a high-speed railway bridge typically utilizes a pile foundation. Revealing the pile–soil interaction mechanism under seismic conditions is essential for the seismic design of these structures. Considering the ballastless track–bridge system of the high-speed railway as the research subject, the pile group foundation model, the equivalent spring foundation model and the pier bottom consolidation model are established. The mechanism of the pile–soil interaction on the bridge system is analyzed using these three models. This research explores the impact of the number of pile foundations on the pile–soil interaction and unveils the influence pattern of the equivalent spring stiffness on this interaction. The findings indicated that the equivalent spring foundation model can be equivalent to the pile group foundation model. The pile–soil interaction effect reduces the natural frequencies of the bridge system and amplifies its dynamic response, with a maximum increase of 130%. When the total cross-sectional area of the pile foundation is constant, the effect of the pile arrangement method on the seismic response of the bridge system is not significant. As the equivalent spring stiffness decreases, the seismic response rapidly diminishes with increasing stiffness; when the equivalent spring stiffness is high, the seismic response tends to stabilize, and the amplitude decreases gradually with increasing stiffness. When the equivalent spring stiffness exceeds [Formula: see text][Formula: see text]N/m, the effect tends to be stabilized, and can be equivalent to 110% of the results of the pier bottom consolidation, which is worthy of consideration in the engineering design.