Coupled DEM-FEM methods for analyzing contact stress between railway ballast and subgrade considering real particle shape characteristic

Abstract

To investigate the stress concentration at the interface between crushed ballast and soil subgrade, this study developed a coupling program of discrete element method (DEM) and finite element method (FEM) using OOFEM and YADE software. Based on the penalty function method, an interface element was introduced for the DEM-FEM coupling simulation. Moreover, an adaptive volume coupling algorithm was proposed to address the unrestricted behavior of the particles across the interface elements. Therefore, the change in the interface contact stress distribution was analyzed in the process of ballast particles penetrating the subgrade soil. Based on the statistical analysis of the ballast shape scanning results, a morphology reconstruction method was adopted to restore the real irregular shapes of the ballasts. Consequently, a DEM-FEM coupling model of a ballasted railway was established and validated through laboratory test results. The meso-scale mechanism revealed the discontinuous characteristics of the contact stress caused by the ballast aggregates. In addition, the adaptive volume coupling algorithm in the case of ballast penetrating subgrade soil was preliminarily proven to be reasonable. This study provides a more accurate approach for calculating the interface stress between ballast and subgrade, which can support a further refined analysis of ballast railway subgrade deterioration.