Abstract

Railway ballast modeling can be performed by different approaches, through continuous or discrete models, which have their comparative advantages and disadvantages, such as excessive volumes of material for testing and calibration steps. This paper aims to adapt and propose the use of the Hybrid Lattice-Discrete Element Method for modeling railway ballast aggregates. The advantages of using this technique for this purpose are: (i) one-step calibration of the rock material from laboratory test results; (ii) simulation of fractures in rock materials; (iii) visualization of micromechanical phenomena, such as particle slippage and fracture modes; (iv) realistic representation of various geometries compared to the conventional use of the Discrete Element Method. First, parameter calibration was performed from laboratory test results on granite rock obtained from the literature. Then, particle generation, Voronoi discretization and packing algorithms were used to build models of railway ballast samples. These models were used to simulate mechanical tests, namely single particle compression, confined uniaxial compression, monotonic triaxial compression and cyclic triaxial compression. There was consistency between the results and the empirical observations reported in the literature. In addition, variations in particle size distribution were observed during the simulations, as well as the causes of failure in each specimen, either by shear or particle breakage, in addition to the fracture modes of the ballast aggregates. By analyzing these elements together, knowledge is obtained about the phenomena occurring inside the railway ballast under different loading conditions, in addition to the results of strength, failure and deformation. Finally, it is concluded that the proposed method is effective for modeling railway ballast, besides being versatile, allowing to simulate the material for different loading configurations and boundary conditions.

中文翻译：

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道碴建模的混合格子离散元法

摘要

铁路道碴建模可以通过连续或离散模型通过不同的方法进行，这些方法各有其相对的优点和缺点，例如用于测试和校准步骤的材料量过多。本文旨在适应并提出使用混合网格离散元方法来模拟铁路道碴骨料。为此目的使用该技术的优点是：（i）根据实验室测试结果对岩石材料进行一步校准；(ii) 岩石材料断裂的模拟；(iii) 微观机械现象的可视化，例如颗粒滑移和断裂模式；(iv) 与传统使用的离散元方法相比，各种几何形状的真实表示。首先，根据文献中获得的花岗岩岩石的实验室测试结果进行参数校准。然后，使用粒子生成、Voronoi 离散化和打包算法来构建铁路道碴样本的模型。这些模型用于模拟力学试验，即单颗粒压缩、受限单轴压缩、单调三轴压缩和循环三轴压缩。结果与文献报道的经验观察结果具有一致性。此外，除了道碴骨料的断裂模式外，在模拟过程中还观察到颗粒尺寸分布的变化，以及每个样本因剪切或颗粒破碎而失效的原因。通过对这些元素进行综合分析，除了强度、失效和变形结果之外，还可以获得不同载荷条件下铁路道碴内部发生的现象的知识。最后得出的结论是，所提出的方法对于铁路道碴建模来说是有效的，而且用途广泛，可以模拟不同载荷配置和边界条件下的材料。