DESIGN FOR RAILROAD BALLAST AND SUBGRADE SUPPORT

It is noted that uniform contact pressure occurs at a depth of 2-2 1/2 times the cross-tie spacing, and that the point pressures are much greater at less than this depth. It has been found in some cases, that a lime modifier layer would be capable of taking tension and spread the load better. Lime modifier has been used by railroads to reduce shrinkage and swelling of expansive clays and increase shear strength which is effective for only a short period of time. The railroad track structure is open to rainfall allowing the lime to leach out with time, and the clay returns to its original expansive unstable condition. It is also noted that common standards of most railroads in the U.S. do not provide sufficient ballast shoulders to spread the load; very small benefit in stabilization of existing subgrade is obtained by increasing thickness of ballast. If a wide shoulder is used against the ballast, it becomes a subballast, and this subballast will spread the load, thereby increasing stability. In addition, increasing ballast thickness of an existing railroad roadbed can be very difficult if roadway crossings, switches, overhead clearances, etc. are involved.

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  • Supplemental Notes:
    • This is a discussion on Proceeding Paper 13471 (January 1978).
  • Corporate Authors:

    American Society of Civil Engineers

    345 East 47th Street
    New York, NY  USA  10017-2398
  • Authors:
    • Newby, J E
  • Publication Date: 1978-11

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Filing Info

  • Accession Number: 00185434
  • Record Type: Publication
  • Source Agency: ASCE Journal of the Geotechnical Engineering Div
  • Report/Paper Numbers: ASCE 14170 Proc Paper
  • Files: TRIS
  • Created Date: Mar 14 1979 12:00AM