Differential subgrade settlement brings corresponding ballasted track settlement under train load,the latter affects train operation safety and comfort.On basis of the existing laboratory tests,a discrete element model consisting of rail,sleepers and ballasted bed was built with the two-dimensional particle flow code (PFC2D) method to analyze how differential subgrade settlement and train load affect track settlement.The results indicated that as subgrade settlement amplitude increases with a certain wavelength,track settlement amplitude increases firstly,then it keeps stable and finally a void occurs underneath sleepers,but the track settlement wavelength keeps stable; the track settlement wavelength can be simply calculated in such way that the subgrade settlement wavelength spreads to upper rail surface with 25°; the effect of train axle load,magnitude and frequency on the track settlement wavelength is small,the effect of dynamic load frequency on the track settlement amplitude is also small,but the effect of dynamic load magnitude and train axle load on the track settlement amplitude is significant.%有砟轨道路基发生不均匀沉降时,在列车荷载作用下,轨面会产生相应的沉降,进而影响列车运行的安全性和舒适度.在已有室内试验研究的基础上,采用二维颗粒流方法建立钢轨、轨枕和道砟的离散元模型,分析了路基不均匀沉降及列车荷载变化对轨面沉降的影响.结果表明:在路基不均匀沉降的波长一定时,随着波幅的增大,轨面沉降的波幅先逐渐增大而后稳定,并最终引起轨枕空吊;而轨面沉降的波长基本不受路基沉降波幅变化的影响,并且可按路基沉降波长以25°向上扩散至轨面进行简化计算;轨枕未出现空吊时,轨面沉降波长受列车轴重、动荷载大小及频率变化的影响很小,轨面沉降波幅受动荷载频率变化的影响很小,但受动荷载大小和轴重变化的影响显著.
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