The analysis of structural behavior of asphalt pavement presented in this paper started some years ago with the detailed study by Ingimarsson of the results of Hybla Valley tests reported by Benkelman and Williams. That study is continued by including all of the test sections and translating the results into terms of the stress reaction or strength developed by each of the pavement components. It was also found desirable to supplement the Hybla Valley tests by another notable program of field testing conducted by the U.S. Army Engineers Waterways Experiment Station at Vicksburg, Mississippi. This investigation featured direct measurement of pressure transmitted to the supporting soil from loads applied at the surface with deflections measured at various depths and lateral offsets. The results reflect the characteristics of pressure distribution and the geometric limits within which a soil of given strength can sustain the stresses imposed by surface loads. Thus these two outstanding investigations provide basic data on stresses in the soil mass or pressure distribution as it is generally known. The Vicksburg tests provide the basis for isolating the lateral distribution of applied load by shear transfer on the perimeter surface through the pavement structure from the load transmitted directly to the subgrade by the central column. These two stress reactions designated as perimeter shear and developed pressure are expressed by the linear equation for bearing capacity used successfully for many years in the design of soil supported structures. The magnitude, sequence of development, and variation in these stress reactions with the size of the bearing area are determined in the analysis of the Hybla Valley field loading tests. The limiting values of these stress reactions and the settlement at which they occur are controlling factors in the structural design of flexible pavements. Results from those test sections at Hybla Valley which were loaded to capacity have been worked out by the solution of sets of linear equations and are reported in the paper. With the quantitative value of these stress limits established, the linear equation can be translated directly into terms of the pavement thickness required to reduce the contact pressure on the pavement surface to the permissible pressure transmitted to the supporting subgrade. The primary objective of this paper was to present observed stress limits in flexible pavements from full-scale field loading tests as the background for design. However, space limitations do not permit more than a brief discussion of the obvious application to flexible pavement design. An example is given of a balanced design in which the full strength of all pavement components are combined assuming flexibility of the pavement structure sufficient to mobilize perimeter shear in unison with the full supporting capacity of the subgrade. Analysis shows that the Hybla Valley test sections were not so designed and the rigidity or high resistance to punching shear of the thick well-constructed bases prevented the most economical combination of subgrade bearing capacity with pressure distribution through the pavement structure. Comparative analysis of this approach with other methods of design and field experience is available but must be presented later. /Author/

  • Supplemental Notes:
    • Presented at the Third International Conference on the Structural Design of Asphalt Pavements, Grosvenor House, Park Lane, London, England, Sept. 11-15, 1972.
  • Corporate Authors:

    International Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Civil Engineering
    Ann Arbor, MI  United States  48104

    International Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Divil Engineering
    Ann Arbor, MI  United States  48104

    Interrational Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Civil Engineering
    Ann Arbor, MI  United States  48104
  • Authors:
    • Housel, W S
    • Ito, J H
  • Conference:
  • Publication Date: 1972-9

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: p. 823-843
  • Serial:
    • Volume: 1

Subject/Index Terms

Filing Info

  • Accession Number: 00261917
  • Record Type: Publication
  • Report/Paper Numbers: Proceeding
  • Files: TRIS
  • Created Date: Oct 22 1974 12:00AM