Random distribution characteristics of peak dynamic stress on the subgrade surface of heavy-haul railways considering track irregularities

Abstract

The dynamic response of the subgrade surface under moving train loads provides information for subgrade settlement prediction, condition evaluation and so forth. In this paper, a 3D dynamic finite element (FE) model that considers the interactions among the wagon, track and subgrade was built. Then, the irregular vertical track spectrum of the three major lines in China was applied to simulate track irregularity. Through numerical calculation, the influence of vertical track irregularity on the dynamic stress of subgrade surface was investigated. The distributions of peak dynamic stresses at three subgrade surface locations (under each of the two rails and at the track center) along the track under the passage of trains with various axle loads were statistically acquired. The normal distributions of the peak dynamic stresses on the subgrade surface were verified. The maximum peak dynamic stresses were forecasted. The results indicated that the dynamic stresses on the subgrade surface were asymmetric along the center of subgrade surface due to the random distribution of track irregularities, and the peak dynamic stresses were found to follow a normal distribution. With the increase of axle load, the dispersion of peak dynamic stresses increased gradually, and the distribution curve of peak dynamic stresses gradually became steeper. The computed peak dynamic stresses aligned well with the field test data, indicating that the 3D dynamic FE model and statistical analysis method were reasonable. The research results will provide a basis for the reliability analysis of the dynamic deformation and accumulated settlement of subgrade surface.