Analysis of vibration mitigation for CFG pile-supported subgrade of high-speed railway

Ground vibrations due to a train moving on the pile-supported subgrade are investigated using a 2.5-dimensional finite element model (2.5D FEM). The equivalent pile wall approach is used to model the piles and soils. Two types of subgrades, with or without cement fly-ash gravel (CFG) piles, are analyzed to evaluate the performance of CFG pile-supported subgrade in mitigating ground vibration. The effects of area replacement ratio aR and pilesoil stiffness ratio Sps on vibration mitigation performance are studied. Results show that the CFG pile-supported subgrade exhibits positive performance in vibration mitigation, and this performance gets better away from the track than near it. The improved subgrade could elevate the critical speed, and the resonance-like amplification of ground vibration as the train runs at the critical speed for the unimproved subgrade is completely excluded. Increasing either the aR or Sps can enhance the vibration mitigation performance. However, there are the critical values of aR = 8.70% and Sps = 138.89, beyond which the vibration reduction performance would no longer be improved.