FIELD OBSERVATIONS OF BALLAST AND SUBGRADE DEFORMATIONS IN TRACK

An extensive instrumentation program has been undertaken at the Facility for Accelerated Service Testing track located at the Transportation Test Center in Pueblo, Colorado, to monitor the performance of ballast, subballast, and subgrade layers under repeated traffic loading. Test sections are involved that contain wooden and concrete ties, tangent and curved track, ballast depths of 36-53 cm (14-21 in), and three different types of ballast. Soil strain gauges were installed in the ballast and subballast layers to measure the vertical and horizontal strains caused by train traffic loading and by track maintenance operations. Vertical extensometers were used to determine the settlement of the subgrade surface, and soil stress gauges at the subballast-subgrade interface were used to measure the vertical stress on the subgrade. The monitoring included both long-term measurements of the permanent strain and deformation accumulated with traffic and dynamic measurements of the elastic response under train loading. The study has provided extensive and unique data on the nature of the deformation response of a track system as a function of various track parameters. The system responded elastically, but nonlinearly, under each repeated axle-load cycle. However, permanent deformation did accumulate and continue to develop even after 667 GN (75 million gross tons MGT) of train load. Most of the readjustment after tamping disturbances occurred within the first 89-178 GN (10-20 MGT) load, with about half complete within 8.9-17.8 GN (1-2 MGT).

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 6-12
  • Monograph Title: Mechanics of track support, piles and geotechnical data
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00315293
  • Record Type: Publication
  • ISBN: 0309029880
  • Files: TRIS, TRB
  • Created Date: Sep 16 1980 12:00AM