3D hydro-mechanical coupling analysis of dynamic characteristics in saturated roadbed of ballastless high-speed railway

Recent field case study shows that the roadbed of ballastless high-speed railway experienced the water induced disease such as excessive fines pumping and even local subgrade-track contact loss affecting the normal operation of high-speed train due to water immersion through gaps of waterproof materials in expansion joints between the concrete base particularly in rainy seasons. However, the study about the dynamic behavior of high-speed railway subgrade involving water is currently rare. Based on the theory of fluid dynamics in porous medium and the vehicle-track-subgrade coupling vibration theory, a 3D hydro-mechanical finite element model was established to evaluate the dynamic responses of saturated roadbed surface layer under the high-speed train loading with the validation by comparing the calculated values and field data. The temporal and spatial characteristics of dynamic behaviors (stress, pore water pressure, seepage velocity, displacement) of saturated roadbed surface layer are fully discussed. Also, the effects of train velocity, permeability, on aforementioned dynamic responses of the saturated roadbed surface layer are evaluated. The study shows that improving the drainage of ballastless track roadbed has a significant effect on minimizing the ballastless track mud pumping, and the influence zone of hydraulic-mechanical coupling is mainly within 0.1 m of the roadbed.