Analysis of dynamic stresses in ballasted railway track due to train passages at high speeds

Abstract

Repeated train passages bring detrimental effects on train operations, especially at high speeds. In this study, a computational model consisting of moving train vehicles, track structure, and track foundation is used to investigate the stress distribution in the track substructure and underlying soil, particularly when the train speed approaches the critical speed via 2.5D finite element method. The numerical model has been validated by in-situ test results from a ballasted high-speed railway. The computational results reveal that the substructure is shown to be effective in reducing the stresses transmitted to the ground; however, a simple Boussinesq approximation is proved to be inaccurate because it cannot properly take account of the effect of multi-layered substructures and train speeds. It is acceptable to assume a simplified smooth track in the analysis model for determining the maximum stresses and displacements for a low-speed railway (⩽100 km/h) but, for a high-speed one, the dynamic amplification effect of track irregularities must also be considered in subgrade design. Analysis of the stress paths revealed that the load speed and track irregularity increase the likelihood of failure for the subgrade; track irregularity can induce many times of principal stress rotations even under a simple single moving load.

概要

目的

研究高速列车荷载作用下有砟轨道路基和地基内部的动应力特征.

创新点

1. 推导有砟轨道的2.5维有限元求解方程. 2. 从应力的角度出发, 确定已有分析模型适用的列车速度范围. 3. 揭示轨道不平顺对路基和地基内部应力大小和应力路径的重要作用.

方法

1. 基于2.5维有限元理论推导出有砟轨道的动力控制方程(公式(20)). 2. 利用秦沈客运专线的现场测试结果验证模型的准确性(图5). 3. 基于验证后的模型, 分析列车速度、 扣件性能及轨道不平顺对动应力的影响.

结论

1. Boussinesq解无法考虑列车速度和实际路基结构对应力的影响. 2. 平顺轨道模型只适用于列车速度不超过100 km/h的情况. 3. 轨道不平顺不仅会增大动应力的强度还会引起多次主应力旋转, 使得土体更加容易被破坏.