Technology Digests / Laboratory Assessment of Fine Migration in Shoulder Cleaned Track

TD22-018

August 1, 2022
Authors
  • Yu Qian
  • Stephen Wilk
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Key Findings

  • Fine migration was observed in SBC track from both laboratory and field tests, implying regular “cleaning” may be able to extend useable ballast life.
  • The amount of fine migration depends on multiple factors, including amount of fines, fine type, and rainfall. Fine migration is most effective when there are still voids in the ballast section for the fines to flow internally through the ballast (Fouling Index (FI) < 30 or granular fines).
  • Regarding fine migration, the results suggest regular SBC will be most effective in tracks where there is a recent introduction of loose fines. An example situation would be “moderately fouled” lines (FI between 15 to 30) with high tonnage/high axle loads, wet climates, poor ballast quality, and/or locations with extensive windblown sand.

Laboratory Assessment of Fine Migration in Shoulder Cleaned Track

MxV Rail (formerly TTCI) partnered with University of South Carolina (UofSC) to investigate fine migration in shoulder ballast cleaned (SBC) track. In 2021 and 2022, UofSC conducted laboratory “flume tests” that allowed UofSC to quantify fine migration in a variety of maintenance and fine-filled ballast conditions. Laboratory test results were compared with the results from an actual test track “Rainy Section” of the Facility for Accelerated Service Testing (FAST®) in Pueblo, CO,1 along with revenue service testing in the central United States. One of the possible benefits of SBC is fine migration or the “cleaning” of fines out of the center of the track. If this cleaning mechanism occurs, SBC can extend the ballast life before undercutting or track renewal is required. SBC may also reduce track geometry degradation in the long-term. As a companion to Technology Digest 2 on the performance of spot SB, this publication documents evidence of…