Abstract This paper presents a study on mitigating the degradation of ballast by placing an under-sleeper rubber pad (USP) beneath a sleeper. Large-scale track process simulation apparatus (TPSA) tests have been carried out on ballast assemblies (with and without USP) subjected to cyclic loadings. Numerical modelling has been performed using a coupled discrete-continuum modelling (coupled DEM-FDM) approach to investigate the role of USP from a micromechanical perspective. Ballast grains are simulated in DEM by bonding of many cylinders together at appropriate sizes and locations; and when those bonds break, they are considered to represent ballast breakage. The capping and subgrade layers are simulated as continuum media using the finite difference method (FDM). Interface elements were developed for transmitting forces and displacements between the discrete and continuum domains. The coupled model is validated by comparing the predicted load-deformation responses with those measured from large-scale TPSA tests. The model is then used to explore changes in the micromechanical aspects of ballast subjected to cyclic loading, including particle connectivity number, contact force distributions, and contact orientations and associated particle breakage. These findings are needed to gain a better insight as to how USPs help to attenuate the load applied in a ballast assembly.

中文翻译：

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用枕下橡胶垫减轻镇流器退化：实验和数值观点

摘要 本文介绍了通过在枕木下方放置枕下橡胶垫 (USP) 来减轻道碴退化的研究。大型轨道过程模拟装置 (TPSA) 测试已在承受循环载荷的道碴组件（有和没有 USP）上进行。已使用耦合离散连续体建模（耦合 DEM-FDM）方法进行数值建模，以从微观机械角度研究 USP 的作用。通过将许多圆柱体以适当的尺寸和位置粘合在一起，在 DEM 中模拟压载颗粒；当这些债券断裂时，它们被认为代表镇流器破损。使用有限差分法 (FDM) 将封盖层和路基层模拟为连续介质。接口元件被开发用于在离散域和连续域之间传递力和位移。通过将预测的载荷变形响应与从大规模 TPSA 测试中测量的响应进行比较来验证耦合模型。然后使用该模型来探索受到循环载荷的镇流器微机械方面的变化，包括颗粒连接数、接触力分布、接触方向和相关的颗粒破损。需要这些发现来更好地了解 USP 如何帮助衰减施加在镇流器组件中的负载。然后使用该模型来探索受到循环载荷的镇流器微机械方面的变化，包括颗粒连接数、接触力分布、接触方向和相关的颗粒破损。需要这些发现来更好地了解 USP 如何帮助衰减施加在镇流器组件中的负载。然后使用该模型来探索受到循环载荷的镇流器微机械方面的变化，包括颗粒连接数、接触力分布、接触方向和相关的颗粒破损。需要这些发现来更好地了解 USP 如何帮助衰减施加在镇流器组件中的负载。