Analysis of Dynamic Characteristics of Railway Subgrade Based on Three-Dimensional Numerical Simulation

To discuss the effect of train axle load and speed on the dynamic characteristics of soil subgrade, a 3D dynamic simulation of the ballast track-subgrade system was made using ANSYS and FLAC3D. In the calculation process, the hysteretic damping was used to simulate the nonlinear characteristics of soil under cyclic dynamic loading. The proposed method was then used to calculate the dynamic stress of subgrade in the field cyclic loading test of the Dazhou-Chendu railway, and the simulation results showed a good agreement with the field measurements. In the conversion between the load vibration frequency and the passenger train speed, the distance between the peaks of the adjacent dynamic stress was simplified as the two bogie spacing of adjacent compartments. On this basis, the effect of passenger train speed on the dynamic property of soil subgrade was investigated. The results indicate that train axle load and speed has a large impact on the dynamic stress of subgrade surface. With an increase in axle load and speed, the saddle-shaped distribution of dynamic stress of subgrade surface is more obvious. However, train speed has little effect on the attenuation law of dynamic stress along the subgrade depth. The dynamic stress is attenuated by 42%-46% in the subgrade surface layer, and the attenuation value can reach 79%-82% after the diffusion of subgrade bottom layer at different speeds.