Discrete Element Analysis Of Mechanical Characteristics Of Railway Ballasts

In order to study the mechanism of deterioration of railway ballasts. The structural features, the basic mechanical behavior, and the evolution are studied. A model used to anticipate the settlement characteristics of ballast is presented based on the evolution of the state and properties of ballast. This model will supply the theory and scientific technique to keep the rail under the preferable condition. This thesis investigates settlement and deformation modulus of railway ballasts under repeated load induced by train, taking advantage of the discrete element method with the irregular shapes of ballasts. Further more, strength, flexibility and macroscopic mechanical properties of railway ballasts are discussed.The aims of this paper are to determine the mechanical behavior and deterioration mechanisms of railway ballasts, and to reveal the deformation of railway ballasts under cyclic loading, kinetic properties of granular ballasts.1. Considering its irregular shape with the incorporation of parallel bonds, the failure process of individual railway ballast applied between flat platens is simulated by discrete element method. The evolution of the particle of the failure is understood and the tensile strength is obtained.2. The load variables under the influence of ballast material, loading frequency and other physical parameters responding to the railway ballast. Therefore, the settlement and Young’s modulus of railway ballasts is studied under repeated loading through ballast box tests and discrete element method. This study shows that DEM is feasible and accurate enough to get the feature of the mechanical characteristics of railway ballasts.3. By simulation of direct shear tests, studying the process of rearranging under external loads, the contact between the particles, sliding and rolling friction process, focuses on analysis of the shear displacement and shear strength under different ballasts contents.4. The shear strength of railway ballast tends to be complex with the appearance of sand. So analysis of the ballasts movement through the velocity field, level displacement field, and the angle of rotation field in the direct process benefits the essence of shear strength both in macro state and deformation mechanisms of railway ballasts.