中文摘要：

论文提出了一种可用于分析土工格栅与道砟颗粒间相互作用的离散元-有限元耦合方法．道砟颗粒采用镶嵌单元模拟，土工格栅采用梁单元计算，并在接触面上实现了离散元和有限元域间力学参数的传递．通过循环载荷作用下的计算，对比分析了土工格栅对道砟颗粒的加固性能．通过加筋后道砟颗粒的直剪试验进一步揭示了土工格栅加固作用的内在机理．结果表明：土工格栅可有效地降低有砟道床横向位移以及顶部沉降量，加筋后道砟材料的内聚力和摩擦角都有所提高．由此可见，土工格栅能够增加道砟颗粒间的自锁作用，提高道砟材料的强度，并有效地阻止剪切带从上部道砟箱向下部道砟箱贯穿．

英文摘要：

Ballast is a special kind of geotechnical materials with obvious discrete characteristics. The non-uniform settlement of ballast resulting from long-term train loadings influences the regularity and stability of ballasted track and threatens the safety of passing trains. Geogrid reinforcement for railway ballast is an effective and economic method to strengthen the ballasted track. The discrete element method （DEM） has advantages in simulating discrete media, especially the ballast material. In order to study the effect of geogrid reinforcement on the ballast, this paper presents a coupled discrete-finite element method to investigate the interaction between geogrid and ballast particles. The clumps are employed to simulate the irregular shape of ballast particles; the beam elements are used to compute the response of geogrid; and the transmission of dynamic parameters on the contact interface is realized between the discrete and the finite element areas. The effect of geogrid reinforcement on the ballasted track under cyclic loadings is ana- lyzed. To further study the mechanism of geogrid reinforcement, direct shear tests are conducted on the reinforced ballast particles. The results indicate that lateral and vertical displacements are both obviously decreased by the geogrid reinforcement. Geogrid can provide ballast particles with horizontal restraint and help to maintain the track geometry. The cohesive force and friction angle of ballast material are both enhanced after reinforced with geogrid. Geogrid can strengthen the interlock between ballast particles, enhance the strength of ballast material and prevent the shear band in the upper box from propagating into the nether box. According to the above conclusions, geogrid reinforcement is a valid technique to enhance the carrying capacity of ballasted track. In the high-speed and heavy-duty railway section, the installation of geogrid in ballast could contribute to enhancing the stability of ballasted track and reducing the maintenance costs. The coupled