Modelling Changes In Railway Vibration Due To Differential Settlement

Under repeated traffic loading, railway tracks experience settlement which occurs in a nonuniform manner along the track. These differential changes in track profile effect the train-track dynamic interaction forces, which can alter track degradation rates and track geometry quality. Ultimately this results in greater ground-borne vibration. Therefore this paper introduces a novel numerical approach to predict future track settlement considering track irregularity evolution. The model combines empirical settlement laws with finite element theory, where the track and ground are modelling explicitly using perfectly matched layers as boundary elements to absorb outgoing propagating waves. A multi-body vehicle model is used to calculate train-track interaction forces, subject to track geometry irregularities. The model is solved using a mixed frequency-wavenumber and time-space approach resulting in an optimised solution procedure, allowing for the track geometry profile to be updated after every load passage. The model is able to account for evolving track profiles, train-track interaction forces and 3D stress fields. After describing model development, a validation shows its ability to compute the evolution of vertical track geometry profile with increasing load passages. It is then shown that train-track dynamic forces increase significantly after differential settlement, and that elevated vibration levels are induced.