Critical Velocity of High-speed Train Running on Soft Soil and Induced Dynamic Soil Response

Abstract The determining of the critical speed under train operation remains difficult due to the complex properties of the track, embankment and ground. In this paper, a dynamic analysis model comprising track, embankment and layered ground was proposed based on the two-and-half-dimensional (2.5D) finite elements combining with thin-layer elements to predict vibrations generated by train moving loads. The track structure is modeled as an Euler-Bernoulli beam resting on embankment. The train is treated as a series of moving axle loads; the embankment and ground are modeled by the 2.5D finite elements. The dynamic responses of the track structure and the ground under moving axle loads at various speeds are presented. The results show that the dynamic response of ground induced by moving constant loads is mostly dominated by train speed and the stiffness of the topsoil. The critical speed of a train moving on an embankment is higher than the Rayleigh wave velocity of the underlying soil, and softer soils results in lower overall critical speed of the system.