United States Department of Transportation
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Mechanics of Ballast Compaction. Volume 2: Field Methods for Ballast Physical State Measurement
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1982-03-01
[PDF-4.65 MB]
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Abstract:Field methods for measuring ballast physical state are needed to study the effects of ballast compaction. Following a consideration of various alternatives, three methods were selected for development and evaluation. The first was in-place density, which provides a direct measure of compaction. An approach involving water replacement in a membrane-lined hold was devised. A reference density test using a steel container and an impact hammer was also developed. The second was a bearing test using a 5-inch-diameter plate. The load for a specified settlement is proposed as a measure of the in-place ballast stiffness. Plaster of paris was found to be the best method for seating the plate on the ballast. The third method involved the resistance of a tie to lateral force. This is the only one of the three used significantly in track studies in the past. The force required to displace the tie by a specified amount was designated as an indirect measure of ballast physical state around the tie. Laboratory tests were conducted to evaluate the factors influencing this force. Appendices to the report describe the apparatus and procedures for the field tests that evolved after considerable field experience with the methods. This report is Volume 2 of the Final Report on the mechanics of ballast compaction.
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