基于改进内切圆法的离散道砟颗粒建模对二维道砟休止角和道床沉降的影响研究

The Impact of Discrete Ballast Particle Modeling Based on Improved Inscribed Circle Method on Two-Dimensional Ballast Angle of Repose and Ballast Bed Settlement

对采用圆盘相切组合建模的方法进行改进,基于真实道砟颗粒二维轮廓,采用分区最大内切圆法建立道砟颗粒离散元内切模型,在内切模型轮廓边缘采用致密小圆盘填充,建立了轮廓精细化模型,并利用同一轮廓采用最密六边形法建立了填充模型;开展道砟颗粒空心圆柱提升的休止角试验,验证模型的正确性并获得模型主要的离散元参数;在此基础上,利用该3种模型在同一道床中填充,进行数值模拟试验,对轨枕施加荷载幅值为5~30 kN,加载频率为5 Hz的余弦荷载,并对道床的宏细观力学特性进行分析.结果表明:轮廓精细化模型保证圆盘之间相切的同时使圆盘为分区最大圆,计算成本低且精细化程度高,并能够更好地模拟颗粒破损;颗粒的形状与摩擦系数对休止角变化较为敏感,精细化建立的模型颗粒堆积成桩性好;道砟颗粒建模的精细化程度对道床性能影响大,轮廓精细化模型与填充模型在休止角试验与道床试验中力学性能相似,前者计算成本低,在二维离散元道床模型中有较好的应用前景.

In this study,we improved the method of combinatorial modelling of disk tangents.Based on the two-dimensional contour of real ballast particles,the discrete element inscribed model of ballast particles was established by the zonal maximum inscribed circle method,the contour refinement model was established by dense small disc filling at the edge of the inscribed model contour,and the filling model was established by the densest hexagon method using the same contour.Then,we carried out the angle of repose test of hollow column lifting of ballast particles to verify the correctness of the model and obtain the main discrete element parameters of the model.On this basis,these three models were used to fill the same ballast bed in numerical simulation experiments,and the macroscopic mechanical properties of the ballast bed were analysed by applying a cosine load with a load amplitude of 5~30 kN and a loading frequency of 5 Hz to the sleeper.It is shown that the refinement of the contour model is computationally efficient and highly refined and can better model particle damage.The shape of the particles and the friction coefficient are sensitive to changes in the angle of repose,and the fine model has a good pile-up performance.The degree of refinement in the modelling of the ballast particles has a large effect on the performance of the ballast bed.The mechanical properties of the refinement of the contour model and the filling model are similar in the angle of repose test and the ballast bed test.The former has lower computational costs and promising application prospect in the two-dimensional discrete element ballast bed models.