ABSTRACT
Uneven subgrade settlement is inevitable due to the uneven soil property, groundwater-level variation and other subgrade diseases. The existence of infrastructure settlement of high-speed railway will lead to the deterioration of track geometry, which is the formation of the initial track irregularity and eventually imposes impact on dynamic interaction of the train-track system. For ballastless track with superior integrity and high rigidity, the ‘hanging area’ where the track structure loses support from the subgrade is likely to be generated. On this account, a semi-analytical method is presented to calculate the settlement-induced track irregularity by taking the nonlinear subgrade support into consideration. Effect of uneven subgrade settlement in terms of the settlement wavelength and settlement amplitude is investigated. Results indicate that for a certain wavelength of subgrade settlement, the magnitude of track deflection is significantly aggravated by the settlement amplitude, and it ultimately remains at a stable level as the settlement amplitude increases to a certain extent. Accordingly, the separation between track supporting layer and subgrade occurs. With respect to the range of settlement-induced track irregularity, it turns out to show a slight diffusion relative to the wavelength of subgrade settlement, and is hardly affected by the settlement amplitude.
