Geotechnical Rheological Modelling of Integrated Train-Track-Bridge System using a Viscoelastoplastic Approach

A comprehensive understanding of train-track-bridge interactions is crucial for assessing the performance and stability of ballasted railway tracks on bridges. Recent advancements in high-speed trains and the challenges posed by heavy-haul freight trains have intensified the concerns regarding passenger safety, comfort, and overall system maintenance. Elastic or viscoelastic models often fail to capture the complex, irrecoverable deformations and long-term degradation observed in ballasted tracks under sustained dynamic loading, leading to inaccuracies in predicting long-term settlement and maintenance requirements. This model specifically employs Hooke’s, Newton’s, and St. Venant’s elements to simulate both vertical and lateral responses of an integrated track-bridge system. The key highlight of this study is the mechanistic integration of St. Venant’s element, whose stress-dependent yielding behavior is defined by the Nor-Sand constitutive model. This integration enables the accurate capture of both time-dependent deformation and the critical irrecoverable, plastic response of the ballast layer, a capability lacking in conventional approaches. The model is validated against experimental studies, demonstrating its ability to accurately simulate both vertical and lateral responses. A comprehensive parametric analysis is conducted to investigate the influence of ballast thickness, axle loads and train speed on the recoverable and irrecoverable vertical and lateral responses of the integrated system. Results indicate that increasing ballast thickness reduces vertical and lateral displacement, while axle load and train speed impact plastic deformation more. The findings highlight the crucial role of track stiffness, differential settlement and track critical velocity in ensuring the stability of the integrated track-bridge system, offering enhanced predictive capabilities for long-term track degradation and informing more robust design and maintenance strategies for high-performance rail infrastructure by distinguishing and quantifying both recoverable and irrecoverable deformations.