Full-scale model tests on ballasted tracks with/without geogrid-stabilization under high-speed train loads

High-speed trains running on ballasted tracks intensify the vibration of ballast layers to a greater extent than conventional passenger trains, bringing detrimental effects on train operations. The geogrid exhibits advantages in the performance improvement of a ballasted track; however, its stabilization effect in real railways under the action of train moving loads at high speeds remains unclear. Herein, full-scale model tests on a ballasted trackbed with and without geogrid stabilization were conducted, and a novel sequential loading system was adopted to apply the train moving loads equivalently onto sleepers of the ballasted track. In the tests, the highest train speeds were 300 km/h for the ballasted track without geogrid stabilization, and 360 km/h for the ballasted track with geogrid stabilization. To monitor the geogrid tension strain under train moving loads, distributed fiber Bragg grating sensors were mounted on the geogrid ribs. It was found that the maximum geogrid tension strain between neighboring sleepers induced by train traffic was 6 times larger than that beneath the sleepers. This observation provides useful information for the design of geogrid stabilization. Wireless SmartRocks were installed in the ballast layer to trace the motions of ballast particles, and the geogrid influence zone in the ballast layer was identified as being at least 15 cm above the geogrid. The dynamic stress at the subballast surface was decreased by about 49% in the stabilized trackbed. The testing results also showed that geogrid stabilization could reduce ballast breakage (Bg) from 14.9% to 2.5% and reduce the permanent settlement of ballast layer by 40%. The experimental results presented in the paper provide a benchmark for geogrid-stabilization modeling and will be referenced for the optimal design of ballasted tracks.