It has been recently reported that ballast comprising differently graded layers helps to reduce track settlement. The main goal of this paper is to provide micro mechanical insight about how the differently layered ballasts reduce the settlement by employing DEM and thus propose an optimum design for two-layered ballast. The DEM simulations provide sufficient evidence that the two-layered ballast works by preventing particles from moving laterally through interlocking of the particles at the interface of the different layers in a similar way to geogrid. By plotting the lateral force acting on the side boundary as a function of the distance to the base, it is found that the walls in the region of 60–180 mm above the base always support the largest lateral forces and therefore this region might be the best location for an interface layer. However, considering the weak improvement in performance by increasing the thickness of the layer of scaled (small) ballast from 100 to 200 mm, it is suggested that it is best to use the sample comprising 100 mm scaled ballast on top of 200 mm standard ballast as the most cost effective solution.

中文翻译：

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箱式试验中两层镇流器的离散元建模

最近有报道说，由不同等级的层组成的道ast有助于减少轨道沉降。本文的主要目的是通过采用DEM来提供有关不同层状镇流器如何减少沉降的微观力学见解，从而为两层镇流器提供最佳设计。DEM仿真提供了足够的证据，表明两层镇流器通过防止颗粒通过在不同层的界面处的颗粒互锁而横向移动，类似于土工格栅。通过绘制作用在侧面边界上的侧向力作为到底座的距离的函数，可以发现在底座上方60-180 mm的区域中的墙始终承受最大的侧向力，因此该区域可能是接口层的最佳位置。然而，