This paper describes studies concerned with the evaluation of the usefulness of elastic theory for predicting the behavior of soil-cement pavements underloading, and with determination of the influence of various thickness of asphalt concrete on the response of such pavements to load. For these studies, two square soil-cement test pavements, each 20 ft by 20 ft in plan and 8.5 in. thick, were constructed on a soft clay subgrade. One of the two pavements was loaded to a level resulting in cracking of the soil-cement layer. Both were tested under repeated loading with 0, 1, 3 and 5 in. of asphalt concrete surfacing. Stresses, strains, and deflections measured in the test pavements were compared with values predicted by both elastic layer and finite element solutions using material parameters determined in the laboratory. For all the repeated load tests, the deflections of the base increased nearly linearly with the plate load, were primarily dependent on the total applied, and tended to decrease with increasing plate size. A similar dependency existed between applied load and vertical stresses recorded in the subgrade. Vertical stresses in the surfacing and in the base directly under the loaded area were, however, primarily governed by the plate pressure, regardless of plate size. Generally, horizontal strains in the base and surfacing increased with increasing plate size for any one plate pressure, and increased with decreasing plate size for any one plate load. For both the cracked and the uncracked pavement, providing 5 in. of asphalt concrete surfacing reduced the deflections of the base by approximately 20 percent; the same reduction was obtained in subgrade stresses. This relatively small reduction resulted because the asphalt concrete course had a stiffness of only about 1/8 that of the soil-cement for the conditions of test. The asphalt concrete had a large effect, however, in reducing the vertical stresses in the base, and also in reducing the horizontal strains, particularly in the upper part of the base. The study showed that both elastic layer theory and finite element analyses can be used to predict pavement performance under loading. In this study, both methods tended to under0estimate vertical deflections, suggesting a potential shortcoming of deflection as a criterion for pavement performance. While both methods were satisfactory for predicting vertical stresses, the finite element solution proved superior in predicting horizontal stains in the surfacing and base, since it permitted the reinforcing effect of the loading plate to be taken into account. Using the finite element analyses with an incremental loading procedure it has also been shown that for a pavement structure with a relatively stiff base or surfacing, assumption of linear stress-strain characteristics of the subgrade is perfectly adequate for analytical purposes. /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:
    • Fossberg, P E
    • Mitchell, J K
    • Monismith, C L
  • Conference:
  • Publication Date: 1972-9

Media Info

  • Features: Figures; References;
  • Pagination: p. 795-811
  • Serial:
    • Volume: 1

Subject/Index Terms

Filing Info

  • Accession Number: 00261919
  • Record Type: Publication
  • Report/Paper Numbers: Proceeding
  • Files: TRIS
  • Created Date: Oct 22 1974 12:00AM