Final Report: Subgrade Stability

Subgrade stability is a term which relates to the strength and deformation properties of the soil. Both properties significantly influence 1) the response of a subgrade to the heavy repeated loading of construction traffic and operations, 2) the ability to place and compact overlying material layers, and 3) the long-term performance of the pavement subgrade. Ideally the subgrade should be strong enough to prevent excessive rutting and shoving, and sufficiently stiff to minimize resilient deflection. In this report a) concepts for characterizing field subgrade stability conditions are developed; b) subgrade stability requirements are established for construction (sinkage and compaction considerations); c) remedial actions (undercut and backfill, moisture-density control, lime treatment of subgrades) for inadequate subgrade stability conditions are described and evaluated; and d) assessment guidelines for considering which remedial procedure(s) should be used for a particular situation are presented. Moisture-density-CBR (California bearing ratio) data for five typical Illinois soils are presented in Appendix A. Appendix B presents a documented hypothesis describing the mechanism of subgrade softening under conditions of high moisture content and heavy repeated loading.

  • Record URL:
  • Corporate Authors:

    University of Illinois, Urbana-Champaign

    Department of Civil and Environmental Engineering
    205 North Mathews Avenue
    Urbana, IL  United States  61801-2352

    Illinois Department of Transportation

    Bureau of Materials and Physical Research
    126 East Ash Street
    Springfield, IL  United States  62704-4766

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Thompson, Marshall R
    • Kinney, T C
    • Traylor, M L
    • Bullard, J R
    • Figueroa, J L
  • Publication Date: 1977-6


  • English

Media Info

  • Media Type: Web
  • Edition: Final Report
  • Features: Appendices; Figures; References; Tables;
  • Pagination: 110p

Subject/Index Terms

Filing Info

  • Accession Number: 01100777
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-IL-UI-169, UILU-ENG-77-2009
  • Created Date: Jun 10 2008 10:31AM