Experimental and Numerical Study of the Dynamic Response of XCC Pile–Raft Foundation under High-Speed Train Loads

Qiang Fu,Jie Yuan

doi:10.3390/app11199260

Abstract

A series of dynamic large-scale model tests and three-dimensional finite element analyses were conducted to investigate the dynamic response of track embankment and XCC pile-raft composite foundation in soft soil for a ballastless high-speed railway under moving train loads. The results indicate that the vibration velocity obtained from the FE numerical simulation agrees well with that from the model test in vibration waveform, amplitude, and frequency characteristics. The peak values corresponding to the passing frequency of train carriage geometry (lc = 25 m), bogie (lab = 7.5 m), and axle distance (lwb = 2.5 m) respectively reflect the characteristic frequencies of the train compartment, adjacent bogie, and wheel load passing through. The peak velocity significantly depends on the distance from the track center in the horizontal direction, of which the attenuation follows the exponential curve distribution. The vibration velocities decrease rapidly within embankment, show a vibration enhancement region from raft to the 1 m depth of foundation soil, then decreases gradually along the subsoil foundation, to a very low level at the bottom of the subsoil, which is much lower than that at the track slab and roadbed. The pile-raft composite foundation can reduce the vibration level effectively and improve the safety of trains running in soft soil areas.

Highlights

The coupled interaction between railway tracks and substructures needs to be properly considered for the design of high-speed railways over soft clays [1,2,3,4,5,6,7], as it tends to result in geotechnical problems, such as a reduction of the bearing capacities of foundations and unexpected settlement
The results show that piles with an X-shaped cross section can provide greater bearing capacity than traditional circular piles with the same section area
The intensity of the vibration velocity curves at each location under the high-speed load is clearly higher than that under the low-speed load, including the amplitude, similarity, and fluctuations of the intensity, which are associated with the increase of the train speed

Summary

Introduction

The coupled interaction between railway tracks and substructures needs to be properly considered for the design of high-speed railways over soft clays [1,2,3,4,5,6,7], as it tends to result in geotechnical problems, such as a reduction of the bearing capacities of foundations and unexpected settlement. The working performance of the railway track, substructures, and underlying soils depends on the properties of individual components, and on the coupled interaction between each other. The train-induced vibration of the track and ground is strongly affected by the relationship between the train speed and the corresponding propagating wave velocity of the supporting media. At the critical speed, moving train loads induce strong vibration in the track structure, and increase the risk of train derailment and track structure damage.

Results

Discussion

Conclusion