LABORATORY EVALUATION OF RUTTING IN BASE COURSE MATERIALS

A method is presented for evaluating the relative performance of unstabilized base course materials with respect to rutting and is then used in the evaluation of a number of materials. A general method is also proposed for calcualting rut depth occurring in flexible pavements. The proposed methods make use of the plastic axial strains obtained from the repeated load triaxial test. Cylindrical specimens 6 in. in diameter and 12 in. in height of crushed stone and soil-aggregate mixtures were placed in a conventional triaxial cell and subjected to 100,000 load repetitions using a constant confining pressure and a triangular stress pulse. Stress-strain curves giving the relationship between deviator stress, confining pressure and plastic axial strain were constructed for each material studied using the repeated load test results. The concept of a rut index was proposed which can be calculated making use of the plastic stress-strain relationship, and is approximately proportional to the rut depth that will occur in the base after a desired number of load repetitions. The rut index appears to offer a practical laboratory method for evaluating the relative performance of base materials used in pavements having similar structural configurations. An evaluation of the test results using the rut index approach indicates that under good conditions of drainage and proper maintenance of the pavement surface, carefully selected blends of 20 percent soil and 80 percent stone should perform satisfactorily. Soil aggregate blends having properties similar to the materials tested should probably not be used at all under poor drainage conditions, and 40-60 blends should not be used even under good conditions of drainage. The results further indicate that only a sufficient amount of fines should be used in a crushed stone base to permit proper compaction if the amount of rutting in the base is to be minimized. Furthermore, even though the specified gradation and density may be the same, bases constructed from aggregates obtained from different sources may exhibit different rutting characteristics. A general engineering method for estimating the rut depth in a flexible pavement after a desired number of load repetitions was proposed which utilizes nonlinear layered theory, the plastic stress-strain response of the component materials, and a hyperbolic, plastic stress-strain law. Field verification is now needed of both the proposed rut index and the general method for predicting rut depth. /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:
  • Barksdale, R D
• Conference:
  • Presented at the Third International Conference on the Structural Design of Asphalt Pavements, Grosvenor House, Park Lane, London, England, Sept. 11-15, 1972.
• Publication Date: 1972-9

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 161-174
• Serial:
  • Volume: 1

Subject/Index Terms

• TRT Terms: Aggregates; Base course (Pavements); Calculation; Deformation curve; Flexible pavements; Index tests; Laboratory tests; Materials; Ruts (Pavements); Soils; Specifications
• Uncontrolled Terms: Computation; Rut
• Old TRIS Terms: Index properties; Materials specifications
• Subject Areas: Geotechnology; Highways; Materials; Pavements;

Filing Info

• Accession Number: 00261964
• Record Type: Publication
• Report/Paper Numbers: Proceeding
• Files: TRIS
• Created Date: Oct 22 1974 12:00AM