Measurements of the distribution of vertical stress in the subgrade for given depths of ballast, track structural configurations and loading conditions are described. The mean maximum vertical stress in the subgrade can be predicted with reasonable accuracy by simple elastic theory. The results of laboratory work in which samples of soil were subjected to repeated triaxial loading are presented. For the cohesive soils tested a level of stress was found above which repeated applications of load caused large permanent deformations and below which permanent deformations were small and terminating. Based on these findings a method of track foundation design is developed in which the depth of ballast required to prevent excessive deformation of the subgrade can be predicted from the results of a simple laboratory repeated load test and a knowledge of the traffic loading to be carried. Small decreases in construction depth from the design depth produce large increases in deformation rate while large increases in construction depth over the design depth produce little return in terms of reduced rates of deformation. The proposed design procedure produces construction depths that are apparently close to the optimum for the fine grained soils so far investigated.

  • Supplemental Notes:
    • This abstract is also contained in "A Bibliography on the Design and Performance of Rail Track Structures", September 1974, RRIS #072794, which was prepared for the Urban Mass Transportation Administration.
  • Corporate Authors:

    Institution of Civil Engineers

    One Great George Street, Westminster
    London,   United Kingdom  SW1P 3AA
  • Authors:
    • HEATH, D L
    • SHENTON, M J
    • Sparrow, R W
    • Waters, J M
  • Conference:
  • Publication Date: 1972

Media Info

  • Pagination: p. 251-267

Subject/Index Terms

Filing Info

  • Accession Number: 00072822
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 11 1976 12:00AM