Stability Analysis of Subgrade under Dynamic Loading of Single and Double High-Speed Railways in Karst Areas

With the increase in the use of high-speed trains, karst collapse disasters have become increasingly prominent during the construction and operation of railway projects. To study the propagation characteristics of vibration wave caused by single and double railways in karst area, as well as the influence of sinkholes on the stability of the roadbed, a coupling model of vehicle-track-subgrade (including underlying sinkhole) considering track irregularity was established based on the geological engineering characteristics of a karst site. The results show that the subgrade stability is controlled by multiple factors related to the upper load, the stability of the caves, and the soil state; increasing the upper load of the track further develops the sinkhole and has a negative effect on the subgrade stability. The amplitude of vertical dynamic displacement on the subgrade surface can reach 1.31 mm under the superimposed effect of the vibration of double railways, which is approximately 50% higher than that of a single railway. Under the long-term cumulative effect of train vibrations, the sinkholes grow faster in dynamic displacement amplitude than the roadbed surface, and will lead to abrupt displacement of subgrade surface.