Dynamics of high‑speed rail ballasted tracks on asphaltic support layers

With the continued expansion of high‑speed rail (HSR) networks, trackbeds must withstand ever‑increasing cyclic loads without compromising safety or serviceability. This study quantifies the dynamic and long‑term performance benefits of incorporating asphaltic support layers (ASLs) beneath conventional ballast. To do so, a two‑stage hybrid model is developed: (1) a MATLAB-based vehicle–track interaction model that yields wheel–rail forces in the presence of measured track irregularities, and, (2) a 3D finite element (FE) substructure model that calculates stresses, displacements, and accelerations throughout the ballast–subgrade system, where asphalt is modeled using a Prony series approach. Field data from the Beijing–Zhangjiakou HSR line are used to validate the model, with simulated stress and vibration amplitudes showing close correlation with the field measurements. Parametric studies show that a 10 cm ASL lowers peak dynamic stresses in the subgrade by ≈ 55% while leaving net vertical deflection virtually unchanged. Increasing ASL thickness from 8 cm to 15 cm further attenuates subgrade stresses, while a 30 °C rise in ambient temperature reduces stress‑reduction efficiency by ≈ 25%. Fatigue and permanent‑deformation analyses demonstrate that all tested thicknesses satisfy a 100‑year design life, and stability checks confirm that subgrade reaction moduli comfortably exceed thresholds commonly used in international standards. A 10 cm ASL therefore offers a balance between asphalt material cost and performance enhancement.