Dynamic performance of high-speed railway formation with the rise of water table

Abstract

This paper presents an experimental study on the influences of water table and train speeds on the dynamic performance of high-speed railway formation using a full-scale physical model testing apparatus. Stationary cyclic loading tests were first conducted to assess the fundamental dynamic performance of railway formation caused by increasing groundwater table. Resilient deformation increased significantly when water table rose from the subsoil bottom to the subgrade surface, and the resonant frequency of the track-formation system decreased from 16Hz to 12Hz. Then moving loading tests simulating train's passages were performed to reveal the dynamic responses of railway formation at train speeds of 5–360km/h, such as the resilient deformation, dynamic soil stress and dynamic pore water pressure. Test results of two kinds of subgrade conditions were presented and compared, i.e., the design condition with the optimum subgrade moisture content and the extreme condition of the submerged subgrade. Combined with the amplification effect of increasing train speeds, the dynamic responses developed faster and larger due to water table rising. The contact pressure distribution under the track structure exhibited the shape of concave parabola for the optimum subgrade, while the distribution pattern presented the shape of letter “W” for the submerged subgrade as the soils around the edges entered into the plastic state. Finally, determination of the subgrade thickness for the design and extreme conditions was discussed, and the design code underestimated the subgrade thickness for the extreme situation in high-speed railways.