Technology Digests / Lateral Track Strength Increase during Maintenance Speed Restrictions

TD24-003

July 8, 2024
Authors
  • Stephen Wilk
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Key Findings

  • The relationship between accumulated traffic and lateral track strength after disturbing ballast involves a linear increase until approximately 0.05 to 0.1 MGT (16.8 percent increase), then the trend shifts to non-linear logarithmic relationship until approximately 10 MGT (44.4 percent increase), and finally, either becomes constant or continues to slowly increase above 10 MGT.
  • The increase in lateral track strength with tonnage is generally related to the initial post-maintenance (0 MGT) strength. This means stronger track (e.g., greater tie and ballast interlock ability) will generally see greater strength benefits from tonnage than weaker track.
  • Lateral tie resistance and vertical track settlement increased with increasing tonnage accumulation, thereby reinforcing the notion that both increased ballast density and interlock are sources of lateral track strength.

Lateral Track Strength Increase during Maintenance Speed Restrictions

MxV Rail performed single-tie push tests (STPTs) at multiple tonnage increments during the initial compaction runs for the newly constructed Facility for Accelerated Service Testing (FAST®) track in Pueblo, CO. The push tests were performed to measure the lateral track strength increase between tonnages of zero and 0.1 million gross tons (MGT) after tamping. The trend from this recent test is combined with previous testing (tonnage increments above 0.1 MGT) to define an entire trend relating to the increase in lateral tie resistance to tonnage. With the full trend available, the level of re-compaction at any tonnage after tamping can be estimated, which may help determine appropriate tonnages at which to release post-maintenance speed restrictions. This Technology Digest focuses solely on the level of ballast compaction—only one of many factors affecting the lateral track strength. A comprehensive review of these parameters has been the subject of previous publications.1,2 This work…