Technical Reports

Trial Low Track Modulus Tests at FAST

  • 01
  • Jun
  • 1995
AUTHOR: Federal Railroad Administration
KEYWORDS: Low track modulus; track performance
ABSTRACT: A study to investigate the influence of low track modulus on track performance under traffic was conducted by the Association of American Railroads, Transportation Test Center, Pueblo, Colorado. A 100-foot trial section of track was constructed to control track modulus. The existing stiff natural silty sand subgrade was excavated, and a 5-foot layer of low stiffness clay was installed providing the low modulus. For a comparison, a control section was established nearby over the natural subgrade, which provided a much greater track modulus. Both sections were monitored to determine the track performance with tonnage accumulation and with maintenance. Of primary interest were the track deflection, stiffness and modulus measurements and how these changed with tonnage accumulation and maintenance. It was determined that as variance in track stiffness along the track increases, differential settlement or track roughness also increases. The factor causing rough track was not the low modulus itself; rather, it was due to the increased variability of track stiffness in the low track modulus section. Although this report is intended to describe the test procedures and present the results in a general manner, a number of very promising leads are suggested by the research. For example, the test illustrated the maintenance forecasting potential which could result from measuring track deflection or stiffness on a moving basis. Also indicated by the test results is the manner in which such data should be measured and analyzed to provide meaningful information to the track maintenance engineer.