Discrete Element Analysis And Experimental Verification Of Railway Ballast Mechanical Characteristics

Traditional ballasted railway track has been used throughout the world. In order to reduce maintenance costs of the ballasted railway track and improve the comfort of passengers, it’s of significant import to further research the railway ballasts material failure mechanism. This paper carried out a series of experiment and made discrete element analysis to research the mechanical properties of railway ballast based on theory of fracture mechanics and discrete element method. The main research includes the following aspects:1. This paper designed and carried out the experiment to determine characteristic strength of railway ballast, and material of the samples are granite. Single ballast with diameters ranging in [20,75] mm was loaded by vertical until fully broken. During the experiment, data acquisition system was used to record the loading force and displacement of the pressure head. The results showed that the fracture strength of ballasts have a certain degree of dispersion, and the failure strength decreases with the increasing of the size of ballast. And then Weibull statistical theory of fracture was used to analysis and calculate the characteristic failure strength.2. In order to numerical simulate crushing behavior and mechanical properties of the railway ballasts accurately, this paper structured actual ballasts precisely. With 3D laser scanning system, we obtained the point cloud information of railway ballasts with actual irregular shape. And through the 3D mesh processing software, the triangle mesh surface is obtained. In the triangular mesh, spherical particles are random packed. In this way, ballast structure model with irregular real shape is simulated with high precision with parallel particle bond.3. Based on the macro mechanical properties of materials obtained by experiment, such as material Young’s modulus and Poisson ratio, this paper determined micro mechanical parameters of railway ballasts, such as particle elastic modulus, stiffness, bond strength etc. through the analysis of calculation. And also discussed the influence of particle stiffness and shear strength on macroscopic parameters of materials in discrete element simulation.4. In this paper, the discrete element method was used to numerical simulate loading crushing process of ballasts. Data including force strain curve, number of bond fracture and so on was analyzed to research the particle breakage mechanism. Through a large scale of calculation both by simulation and loading experimental verification, it is found that:with the increase of the size of ballast, the compressive strength decreases gradually. And based on the Weibull statistical theory, the characteristic strength and Weibull modulus was obtained. The results of experiment and numerical simulation are consistent. At the same time, the simulation of multi-channel ballast particles in the ballast box by compression load was calculated, and particles breaking rate, the overall displacement and failure form etc. was analyzed. The results showed that the ballast particle breakage and displacement increase with the increase of ballast size.