Concrete slab tracks help shield the supporting railway earth structure from external water ingress. However, the inevitable cracks that arise during its lifespan provide a pathway for water penetration, leading to changes in the degree of saturation of the underlying support. This can affect the dynamic response of the structure, however is challenging to model due to the computational requirements of three-phase unsaturated soil simulation. To address this, this paper presents two main novelties: 1) an efficient moving frame of reference approach for railway ballastless tracks on unsaturated earthworks subject to train loading, 2) new findings into the effect of degree of subgrade bed saturation on ballastless track dynamics. First the model is presented, including formulations for vehicle-track interaction and unsaturated subgrade dynamics. Considerations for numerical stability are then discussed and the model is validated, before investigating the role of subgrade bed saturation on pore water pressure and displacements. It is shown to have a high impact on pore water pressure generation, but a limited impact on deflections. The effect of train speed is then investigated and it is found that higher train speeds induce higher pore water pressures. Track irregularities are also investigated and it is found that they play an important role in pore water pressures.

中文翻译：

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无砟铁路轨道在非饱和路基上的动力学建模


混凝土板轨道有助于保护支撑铁路土结构免受外部进水的影响。然而，在其使用寿命期间不可避免地出现的裂缝为水渗透提供了途径，导致底层支撑的饱和度发生变化。这可能会影响结构的动态响应，但由于三相非饱和土模拟的计算要求，建模具有挑战性。为了解决这个问题，本文提出了两个主要的新颖性：1） 在受火车载荷影响的不饱和土方工程上铁路无砟轨道的有效移动参考框架方法，2） 路基床饱和度对无砟轨道动力学影响的新发现。首先，给出了模型，包括车辆-轨道相互作用和非饱和路基动力学的公式。然后讨论了数值稳定性的考虑因素并验证了模型，然后研究了路基床饱和度对孔隙水压力和位移的影响。它对孔隙水压力的产生影响很大，但对挠度的影响有限。然后研究了列车速度的影响，发现较高的列车速度会引起更高的孔隙水压力。还调查了轨道不规则性，发现它们在孔隙水压力中起着重要作用。