Full-Scale Model Testing on Ballasted High-Speed Railway: Dynamic Responses and Accumulated Settlements

High-speed trains generate much higher vibrations in track structures than conventional trains and intensive train passages (e.g., on the Beijing–Shanghai high-speed railway line where the train passage interval is less than 5 minutes) cause accumulated permanent settlement in the railway track substructures, which will decrease track performance and jeopardize the safety of trains. Since very few field measurements on ballasted high-speed railways are available in literature, this paper presents experimental results of vibration velocity, dynamic soil stress, and the accumulated settlement of a ballasted high-speed railway from a full-scale model testing facility with simulated trains moving loads at various speeds. A portion of a realistic ballasted railway consisting of track structure, ballast layer, subballast, embankment, and piled foundation was constructed in a larger box. An eight-actuator sequential loading system was used to generate equivalent vertical loadings on the track structure for simulating the dynamic excitations due to train movements. Dynamic stresses measured in the track substructure layers (ballast, subballast, and embankment) were found to be strongly dependent on train speeds especially for speeds higher than 144 km/h. It was found that both the vibration velocity and the dynamic soil stress were greatly amplified as the train speed increased to 300 km/h, and the ballast layer effectively reduced the vibrations transmitted from the track structure to underlying soil. The accumulated settlement of the substructure did not reach a stable state even after 100,000 moving train loads at a speed of 300 km/h.