Numerical Analysis of the Dynamic Response of EPS Geofoam Railway Embankment to High-Speed Train Load

The construction of high-speed railway lines on weak or compressible foundations continues to pose significant challenges for track stability, serviceability and long-term performance. Excessive settlement and insufficient bearing capacity in the subgrade can compromise track alignment. These conditions may also increase maintenance requirements and elevate both technical and economic risks. Lightweight inclusions such as Expanded Polystyrene (EPS) geofoam provide a technically efficient alternative to conventional ground improvement methods by reducing stress transfer to weak subgrades while maintaining structural integrity. In this study, the dynamic behavior of EPS geofoam–reinforced railway embankments under high-speed train loading was numerically investigated, with specific emphasis on vibration mitigation and vertical displacement control. A three-dimensional finite element model of the track–embankment system was developed and verified in MIDAS GTS NX software. The numerical model explicitly incorporated the railway track system and embankment layers. Realistic material properties for ballast, the load distribution slab (LDS), and EPS layers were used. The model was validated against published field measurements.

Sensitivity analyses were conducted to investigate the effects of train speed and ballast stiffness on dynamic responses, including peak particle displacement (PPD), velocity (PPV) and acceleration (PPA). The novelty of the study lies in the field-validated three-dimensional track–embankment–ground model, mechanistic investigation of EPS geofoam in high-speed railway embankments, and quantitative design-oriented evaluation under realistic operational conditions. Results indicated that the system response was dominated by low-frequency, quasi-static behavior associated with axle loading. Displacement, velocity, and acceleration amplitudes decrease with depth and lateral distance from the track centerline. Pronounced attenuation was observed across the LDS–EPS39 interface (~0.7 mm) and peak reductions of 2.2 mm and 1.7 mm in EPS22 and EPS29 layers, respectively. Railhead displacement remained within 1–2 mm, while rail-base displacement ranges from 5–6 mm over train speeds of 30–97 m/s, indicating stable track–vehicle interaction. Increasing train speed amplified dynamic response, with surface vibrations near the track exceeding the human comfort threshold of 80 dB for speeds above 30 m/s. Moderate ballast stiffness increases (300–600 MPa) provided limited improvement, whereas substantial enhancements (1200–2400 MPa) reduced vibration amplitudes by 2–3 dB, emphasizing the critical role of track–soil interaction. Surface vibration was attenuated by up to 40 dB with lateral distance, while longitudinal patterns exhibited constructive and destructive interference due to periodic axle loads. Overall, EPS geofoam inclusions effectively mitigate dynamic responses in high-speed railway embankments on soft soils, providing quantitative guidance for speed-dependent and material-informed design strategies that enhance operational performance, passenger comfort, and structural safety.