Technical Reports

Ballast Testing at FAST: 1976-82

  • 01
  • Aug
  • 1984
AUTHOR: J. Heiss
SUBJECT: Rail and Infrastructure Integrity
KEYWORDS: Ballast Depth, Shape Factors, Stress and Strain, Ballast Shoulder Width, Geotextiles, Gradation,
ABSTRACT: The railroads, for whom ballast has long been a subject of serious study, have sought to develop criteria for choosing, maintaining, and predicting ballast performance in revenue track. During 1976-1982, two studies (Ballast I & II) were conducted on sections of the FAST loop at the Transportation Test Center (TTC), Pueblo, Colorado. Ballast I research on Depth, Shoulder Width, Material Type, and substructure deformations confirmed many characteristics seen in revenue track, and provided valuable experience in the conduct, per se, of such testing. Findings implied that excess depth can be detrimental to geometry stability (that increasing shoulder width improved profile stability but had little or no effect on horizontal track stiffness) and confirmed the need to distinguish between specific geologic sources for like ballast types with common "generic" names. The AREA/Talbot method for finding subgrade stress was found adequate for design purposes under the conditions investigated. Ballast II extended the 'type' studies and focused on ballast deformation, stress and strain, gradation and particle shape and (to a limited extent) geotextile performance. Ballast with larger, elongated particles, broader gradation, and low flakiness evidenced better performance. Geotextile results showed a need for heavier weight fabrics. The Los Angeles Abrasion test proved questionable for predicting in-track degradation. A Bibliography of ballast-related studies is appended.