Numerical investigation on dynamic behaviour of critical zones in railway tracks under moving train loads

Abstract

The critical zones along a railway line, such as bridge approaches, are areas of serious concern for infrastructure managers owing to their high susceptibility to accelerated track geometry degradation. To improve their performance, a comprehensive evaluation of their response under realistic train-induced loads is paramount. With this objective, the dynamic behaviour of a standard track-bridge transition under moving loads (involving wheel translation and rotation) is investigated through finite-element (FE) analyses. First, a three-dimensional (3D) FE model of a bridge approach is developed and validated against published field data. The validated model is employed to gain insights into the phenomena such as unsupported sleeper formation and principal stress rotation in track substructure elements. The adequacy of 3D cellular geoinclusions in improving the performance of critical zones is also assessed. The results reveal that train parameters (axle load, speed, wheel translation and rotation) significantly influence the stresses, displacements, and sleeper-ballast gap size. The presence of a weak subgrade near the bridge exacerbates the differential movement problem and increases the sleeper-ballast gap size. The findings from this study significantly contribute towards an improved understanding of the response of critical zones, especially the spatiotemporal stress variations, unsupported sleeper formation and influence of geoinclusion reinforcement.