Coupled hydraulic-mechanical-air simulation of unsaturated railway embankment under rainfall and dynamic train load

Abstract

Performance evaluation of the embankment subject to climate change and dynamic train loads is important to the safety of high speed railway (HSR). In this study, based on an elasto-plastic unsaturated soil model, a coupled hydraulic-mechanical-air finite element analysis method is proposed, which integrates the analysis under rainfall condition and the analysis under dynamic load in one numerical simulation. A finite element analysis program called DBLEAVES-X is improved from its previous version (DBLEAVES) to consider the hydraulic-mechanical-air coupled behavior in unsaturated soils under dynamic condition. In order to verify the feasibility of the proposed method, a reduced-scale model test was first simulated. The calculating results showed that the measured displacement and acceleration can be well reproduced by the proposed method. Analyses on the effect of rainfall conditions, train loads and embankment materials were then conducted for a full scale prototype model of typical HSR embankment. The results of the analyses show that higher intensity of rainfall infiltration increases the risk of local failure. A higher train speed and heavier train axle load result in larger displacements. The frequency of the acceleration response is only influenced by the train speed. The embankment performance worsens with the degradation of the embankment material. Preceding rainfall condition results in a larger displacement of the track slab after the dynamic load is applied.