Dynamic analysis of water-rich heavy haul railway tunnels considering basement defects evolution and train effects

Abstract With the rapid development of heavy haul railway transportation technology, tunnel foundation defects and their effects on structural performance have attracted wide attention. This paper systematically investigates the evolution mechanism of tunnel foundation defects in heavy haul railway tunnels and their impact on structural stiffness degradation through experiments and numerical simulations. A heavy haul train–ballasted track–tunnel basement–surround rock dynamic interaction model (TTTR model) is constructed. Firstly, the study reveals the four-stage evolution process of initial defects in the tunnel basement under complex environmental conditions. Experiments were conducted to measure the load-bearing capacity and stiffness degradation of the tunnel basement structure under different defect states. It is found that foundation defects, especially under the coupling of loose fill in the basement with the water-rich environment of the surrounding rock, significantly reduce the stiffness of the tunnel bottom structure and increase the risk of structural damage. Then, based on refined simulation of wheel–rail interaction and multi-scale coupled modeling technology, the TTTR dynamic interaction model was successfully constructed, and its validity was proven through numerical validation. A time-varying coupling technique of constrained boundary substructures (CBS technique) was adopted, significantly improving computational efficiency while ensuring calculation accuracy. The study also analyzes the effects of different degrees of void defects on the dynamic behavior of the train and the dynamic characteristics of the tunnel structure. It finds that foundation defects have a significant impact on the train’s operational state, track vibration displacement, and vibration stress of the tunnel lining structure, especially under the coupling effect of basement voids and the water-rich environment, which has the greatest impact. The research results of this paper provide a theoretical basis and technical support for the maintenance and reinforcement of tunnel foundation structures.