United States Department of Transportation
i
Mechanics of Ballast Compaction. Volume 3: Field Test Results for Ballast Physical State Measurement
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1982-03-01
[PDF-3.93 MB]
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Abstract:The important mechanical processes which influence the ballast physical state in track are tamping, crib and shoulder compaction and train traffic. Three methods of assessing physical state were used at four railroad sites to obtain needed data on the effect of these processes. The methods were: ballast density test, plate load test, and lateral tie push test. The available information from previous studies was also compiled and compared to the new information gathered in this study. The primary objective of this research was to evaluate the usefulness of crib and shoulder compaction in the maintenance of track. The research showed that the effects of tamping and compaction on ballast state depend significantly on the state existing prior to maintenance. For a track in service, tamping generally loosens the ballast. Crib and shoulder compaction primarily densifies the crib, but it also improves the ballast stiffness under the tie. Train traffic had the most influence on ballast physical state. After loosening from tamping, the ballast again reaches its stable physical state within 20 MGT of train traffic. Adding crib and shoulder compaction produced the same physical state as about 0.2 MGT traffic, and the effects of this compaction were not distinct from tamped-only track after about 2 MGT of traffic.
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