Research Results

High-Speed Passenger Rail Tie-Ballast Interaction

  • 13
  • May
  • 2015
AUTHOR: Federal Railroad Administration
REPORT NUMBER: RR 15-13
SUBJECT: Passenger Rail
KEYWORDS: High-Speed Passenger Rail Tie-Ballast Interaction; Track transition; Differential movement; Tie-ballast interaction; Tie-ballast gap; Accelerometers; Cameras
ABSTRACT: This Research Results Report presents evidence of poor tie support and increased applied loads that were used to determine the “root cause” of transient and permanent vertical displacements at two Amtrak bridge transitions. These results are from a Federal Railroad Administration (FRA) study on differential movement at high-speed track transitions. Data from instrumented high-speed passenger bridge transitions along Amtrak’s Northeast Corridor (NEC) near Chester, Pennsylvania show a relation between measured permanent vertical displacements of ballast and a gap between the bottom of the tie and top of the ballast. The existence of a gap at locations experiencing large permanent ballast displacements suggests that poor tie support amplifies the applied loads to the ballast which accelerates ballast and tie degradation. Therefore, the “root cause” of permanent vertical displacements at the instrumented high-speed passenger transition zone locations is concluded to be an increase of applied loads to the ballast and adjacent ties resulting from poor tie support at the instrumented tie.
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