With the evolution of railway infrastructure towards accommodating higher speeds and heavier loads, the under sleeper pad (USP) has emerged as a critical component in mitigating the deterioration of the ballast bed and reducing maintenance requirements. This study aims to enhance the understanding of the suitability of the USP for railway lines and to investigate the static and dynamic mechanical behaviors of the ballast bed (with USP) under the train load. To achieve this, the study conducts on-site tests and employs the discrete element method-multi-flexible body dynamics (DEM-MFBD) coupling analysis to develop a three-dimensional high-fidelity model of the ballast bed (with USP). This comprehensive analysis assesses the impact of varying train speeds and axle loads on the mechanical properties of the ballast bed with the USP, integrating both macroscopic and microscopic perspectives. The results show that there is an 8.54% reduction in longitudinal resistance of the ballast bed (with USP) compared to the ballast bed (without USP), yet it still fulfils the requirements of heavy railway lines. The ballast bed (with USP) exhibits significant improvements in vibration-damping performance, with the wheel-rail vertical force showing a reduction of 8.71% relative to the ballast bed (without USP). This suggests a potential extension of the track structure's lifespan. An increase in train speed markedly influences the vibration levels of the ballast bed (with USP), leading to an increase in ballast bed acceleration by 119.39%. The increase in train axle load demonstrates a minor effect on the plastic deformation of the ballast bed, indicating the ballast bed (with USP)'s capability to accommodate heavier axle load trains.

中文翻译：

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速度和轴重对轨枕垫下道床静态和动态力学性能的影响

随着铁路基础设施朝着适应更高速度和更重负载的方向发展，轨枕垫板 (USP) 已成为减轻道床磨损和减少维护要求的关键组成部分。本研究旨在加深对 USP 对铁路线适用性的了解，并研究道床（使用 USP）在列车荷载下的静态和动态力学行为。为了实现这一目标，该研究进行了现场测试，并采用离散元法-多柔体动力学（DEM-MFBD）耦合分析，开发了道床三维高保真模型（具有USP）。这项综合分析结合了宏观和微观的视角，评估了不同的列车速度和轴荷对 USP 道碴床机械性能的影响。结果表明，与道床（无USP）相比，道床（有USP）的纵向阻力降低了8.54%，但仍然满足重载铁路线路的要求。道床（采用USP）的减振性能显着改善，轮轨垂直力相对于道床（未采用USP）降低了8.71%。这表明轨道结构的使用寿命有可能延长。列车速度的增加显着影响道床的振动水平（根据USP），导致道床加速度增加119.39%。列车轴荷的增加表明对道床的塑性变形影响较小，表明道床（采用 USP）能够适应较重的轴荷列车。