Investigation of a dynamic chord method and its application on track irregularity evaluation and track maintenance

Abstract

Track irregularity causes dynamic train-track interactions and accelerates the degradation of their components. In this paper, we proposed a dynamic chord method based on dynamic measurements that can be directly used for maintenance planning. Based on the extensive investigations, we found that the results from the dynamic chord method are comparable to the static chord measurement results with appropriate cut-off wavelength and chord length. Specifically, the maximum chord lengths to apply on the dynamic measurements with cut-off wavelengths of 42 m, 70 m, and 120 m are 20 m, 30 m, and 40 m respectively. Track settlement can be identified based on the difference analysis between the static and dynamic chord results when the chord length is larger than the maximum chord length. Further, we proposed a method to evaluate track stiffness based on the peak differences between static and dynamic measurements. A threshold of 2 mm is used to determine whether there are track stiffness anomalies. The validity of the method is shown with experimental tests and field validations. Finally, a more direct method to guide track adjustment based on dynamic measurement is proposed. The application of this method on track adjustment shows that the amplitude of dynamic longitudinal level and the standard deviation reduces by 42 % and 51 % respectively. Periodic longitudinal level at the wavelength of 32 m, due to the bridge span, also sees significant improvements.