Technical Reports

Development of a Structural Model and Materials Evaluation Procedures- Ballast and Foundation Materials Research Program

  • 21
  • Nov
  • 1975
AUTHOR: Q.L. Robnett, M.R. Thompson, R.M. Knutson, S.D. Tayabji
KEYWORDS: Structural Analysis Model; Finite Element Method; Track Support System; Ballast; Material Testing
ABSTRACT: An adequate engineering analysis of conventional railway track support system (CRTSS) requires the consideration of all the major components of the track support system. Past efforts in this area have not been satisfactory because of lack of proper material characterization and very simplified modelling of the CRTSS. An attempt has been made to model the CRTSS using the finite element method that would allow a determination of the transient response of the CRTSS by incorporating proper material characterization. Because of the complex three-dimensional geometry, the analytical modelling was divided into two stages; namely, a longitudinal analysis stage and a transverse analysis stage. Stress dependent material properties of the ballast, the sub-ballast, and the subgrade can be used with the finite element method. The finite element model has been validated using the measured response at Section 9 of the Kansas Test Track. Good agreement was obtained between the measured response and that calculated using the finite element model. The report also describes ballast and subgrade materials evaluation procedures. The repeated load tri-axial testing procedure that has been selected for evaluating the resilient and permanent deformation characteristics of ballast and subgrade soil materials is described in detail.