Evaluative tests for strength of compacted subgrade soils are often highly empirical, e.g., CBR, or yield data which are neither fundamental nor consistent with established principles of theoretical soil mechanics. Fundamental stress strain and shear strength data for partially saturated compacted soil is best obtained from triaxial test methods for controlling or monitoring relevant state variables and synthesizes data generated into a compact parametric form for design of flexible pavements. Two constant strain rate triaxial procedures with sigma 3 = 30 psi are defined; a consolidated-constant water content test with sample volume measurement and consolidated-undrained saturated test. These procedures yield fundamental data for five partially saturated, compacted, fine-grained, Nebraska soils. Laboratory stress strain curves are well modeled by Kondner's two constant hyperbolic stress strain function. Exponential function correlations exist between the hyperbolic constants a and b and the state variables of void ratio and percent saturation. Using correlated synthetic stress strain curves can be generated which model soil behavior for any density between Proctor and modified Proctor for degree of saturation from 60-100 percent. Using these correlations, flexible pavement design methods requiring laboratory subgrade stiffness can be utilized for any assumed insitu subgrade condition of the soils tested after a single laboratory validation test.

  • Supplemental Notes:
    • Prepared in cooperation with Nebraska Department of Roads and FHWA.
  • Corporate Authors:

    University of Nebraska, Omaha

    Department of Civil Engineering, 6001 Dodge Street
    Omaha, NE  United States  68182-0178
  • Authors:
    • Sneddon, R V
  • Publication Date: 1975-6

Media Info

  • Pagination: 53 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00139818
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: NE-DOR-R-75-1 Final Rpt.
  • Contract Numbers: 63-14
  • Files: TRIS, USDOT
  • Created Date: Oct 6 1976 12:00AM