An experimental analysis of dynamic deformation and settlement resistance in a novel prestressed railway subgrade

The dynamic deformation characteristics of track-subgrade systems under moving train loads provide valuable insights for vibration and serviceability assessment of the track-subgrade. This study developed three 1:5 scale track-subgrade models incorporating the novel prestressed subgrade structure and conducted two series of dynamic tests to examine how the heavy-haul train axle loads and prestress levels affected the track-subgrade dynamic deformation. The primary frequency of the subgrade dynamic displacement was observed closely aligned with the input loading frequency of 2 Hz, indicating the validity of the test setup. The track-subgrade dynamic displacement decreased with increasing distance from the loading source, of which the elastic deformation near the subgrade shoulder attenuated by approximately 79% compared to that at the sleeper end. The elastic deformation at the monitoring points approximately linearly increased with the axle load at rates ranging from 0.0018 to 0.0029 mm/t. Conversely, increasing prestress reduced the track-subgrade elastic deformation with average rates of 22.8 and 1.63 μm/100 kPa at the sleeper end and subgrade shoulder, respectively. Furthermore, application of prestress enhanced the track stiffness, with the equivalent track stiffness rising by 16.3% and 17.7% when the prestress increased from 0 to 50 kPa and from 50 to 100 kPa, respectively. The study also showed that the prestressed reinforcement structures could significantly mitigate the cumulative track-subgrade settlement over 60%, comparing the prestressed subgrade with 50 kPa prestress to the unreinforced subgrade, which highlighted the superior deformation resistance of prestressed subgrades under the train loads.