Investigation on vibration mitigation performance of CFG pile-reinforced subgrade for high-speed railway

For investigating ground vibrations and mitigation performance of the CFG pile-soil composite subgrade under high-speed train loading, firstly, based on the 2.5-dimensional finite element method(2.5D FEM) and equivalent pile walls approach, the 2.5D FE model for track-embankment-CFG pile-soil composite subgrade system was established. Secondly, the reliability of the model was validated by comparing with the field measurements. Finally, by taking the vertical vibration acceleration as a primary indicator and considering various vehicle speeds, the influence of CFG pile design parameters on vibration mitigation performance was investigated by comparing the ground vibration at different pile diameters, pile spacing, and pile stiffness. The results show that, compared with the unreinforced subgrade, the CFG pile-reinforced subgrade exhibits favorable vibration mitigation performance, and this performance is better at a distance from the track than near it. In the near track zone, the vibration mitigation performance depends on both the vehicle speed and resonance conditions. The vibration mitigation performance increases with the increase of pile diameter or the increase of pile stiffness or the decrease of pile spacing. However, it is hard to further improve the vibration mitigation performance when d(pile stiffness) ≥1/4s(pile diameter), or s≤4d, or RPS(pile-to-soil stiffness ratio)≥138.9. The CFG pile-reinforced subgrade increases the critical speed, and the vibration mitigation performance deteriorates when the train runs at the critical speed. © 2023 Central South University of Technology. All rights reserved.