Analysis of the breakage parameters of railway ballast based on the discrete element method

目的 有砟轨道在长期服役下频繁出现道砟颗粒掉角、破碎等劣化现象,降低了有砟轨道的稳定性。而道砟的破碎与其形状、大小、应力状态等有较大的关系,因此合理确定道砟的破碎参数是研究和解决这一问题的关键。本文旨在探索基于Hertz-Mindlin本构模型的道砟破碎参数,研究道砟的破碎性能,以期为实际服役的铁路有砟轨道提供参考。 创新点 1. 采用统计学方法分析了道砟破碎的主要影响因素及其临界压碎强度和临界剪碎强度;2. 采用响应面法确定了离散元道砟的最优破碎参数组合;3. 通过直剪试验分析了道砟的抗剪性能和破碎状况,为实际服役的有砟轨道提供参考。 方法 1. 通过单轴压缩破碎和单轴剪切破碎实测试验,确定简单应力状态下道砟破碎的主要影响因素及其临界压碎强度和临界剪碎强度（图1和2,表3）;2. 建立可破碎道砟的精细化离散元模型,采用Box-Behnken法进行仿真试验的工况设计,并对仿真试验结果进行响应曲面分析以获取最优破碎参数（图9,表7）;3. 通过对比实测与仿真的直剪试验结果,验证离散元道砟破碎参数的正确性,并探明道砟堆积体的抗剪性能（图12和13）。 结论 1. 对于粒径范围为22.4~63.0 mm的道砟,其压碎特征应力和剪碎特征应力受道砟粒径的影响不大,而受道砟形状的影响较大;2. 针状道砟更容易破碎;3. 直剪试验中,道砟的累积破碎率逐渐增大,最终达到13.97%;4. 道砟的最优破碎参数可参考本研究的结论进行取值,且具有较高的应用价值。 During the service lives of ballasted tracks, the ballast experiences degradation, such as breakage and fragmentation, which reduces the stability of the tracks. Ballast breakage is directly related to the shapes, sizes, and stress states of particles. The key to solving this problem is to determine the breakage parameters of railway ballast. In this study, through uniaxial compression and uniaxial shear tests, the factors associated with ballast breakage for a simple stress state were obtained. Then, a refined discrete element model of railway ballast was established. The Box-Behnken method was used to design a simulation test, and a response surface method was used to obtain the optimal ballast breakage parameters. Lastly, the results of a direct shear test were compared with the simulation results to verify the correctness of the parameters and to study the shear resistance of the ballast aggregates. The results showed that for ballast particles with sizes of 22.4–63.0 mm, the characteristic stresses of compression and shear were not significantly affected by the size of the particles, but were greatly affected by their shape. In particular, long particles were more likely to break. During the direct shear test, the cumulative ballast breakage ratio gradually increased to 13.97%. The optimal breakage parameters of the ballast determined by this approach have high application value in the management of ballasted tracks.