Track Performance in Tunnels and Rail Transition Areas with Under Tie Pads and Under Ballast Mats

Under tie pads (UTP) and under ballast mats (UBM) have been increasingly used in rail track construction to reduce maintenance costs by better distributing loads, reducing the track modulus, and increasing ballast contact areas with ties. Locations such as tunnels, bridges, and bridge approaches are especially strong candidates for UTP and UBM use due to the high support stiffness they provide to the ballast. In this study, the Virginia Avenue Tunnel in Washington D.C. was instrumented during construction to monitor track pressure distribution, tie acceleration, and tunnel floor vibration during the first 20 months of use. It was found that UTP and UBM reduced the track modulus. Use of UBM in lieu of an extra 6 in. of ballast was found to result in more than a 10% reduction of the average force on the tie directly under the train axle, providing much better distribution of pressure across ties. Settlement measurements showed that the track settlement occurred over the first 6 months of measurement, after which it stabilized to less than 0.157 in. (4 mm).


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos; References; Tables;
  • Pagination: 15p

Subject/Index Terms

Filing Info

  • Accession Number: 01764159
  • Record Type: Publication
  • Report/Paper Numbers: TRBAM-21-00274
  • Files: TRIS, TRB, ATRI
  • Created Date: Dec 23 2020 11:21AM