Physical modeling of long-term dynamic characteristics of the subgrade for medium–low-speed maglevs

To investigate the dynamic characteristics and long-term dynamic stability of the new subgrade structure of medium–low-speed (MLS) maglevs, cyclic vibration tests were performed under natural and rainfall conditions, and the dynamic response of the subgrade structure was monitored. The dynamic response attenuation characteristics along the depth direction of the subgrade were compared, and the distribution characteristics of the dynamic stress on the surface of the subgrade along the longitudinal direction of the line were analyzed. The critical dynamic stress and cumulative deformation were used as indicators to evaluate the long-term dynamic stability of the subgrade. Results show that water has a certain effect on the dynamic characteristics of the subgrade, and the dynamic stress and acceleration increase with the water content. With the dowel steel structure set between the rail-bearing beams, stress concentration at the end of the loaded beam can be prevented, and the diffusion distance of the dynamic stress along the longitudinal direction increases. The dynamic stress measured in the subgrade bed range is less than 1/5 of the critical dynamic stress. The postconstruction settlement of the subgrade after similarity ratio conversion is 3.94 mm and 7.72 mm under natural and rainfall conditions, respectively, and both values are less than the 30 mm limit, indicating that the MLS maglev subgrade structure has good long-term dynamic stability.