Effect of Geosynthetics on Structural Pavement Design

Properly installed geosynthetics have been proven to generate cost savings and improved performance of aggregate base courses used in highway pavement construction. Other advantages include the ability to extend pavement service life without increasing pavement thickness and without sacrificing performance. While many agencies are currently using geosynthetics, there is a significant lack of understanding of the fundamental properties of these materials; thus, designers are often forced to rely on conservative estimates when considering the contribution of geosynthetics in the performance of the pavement structure. A deeper understanding of the interactions between geosynthetics and aggregate base courses is needed, as well as a more fundamental method for incorporating the properties of geosynthetics into existing pavement design practices. To this end, the effects of geosynthetics should be quantified with respect to (1) the improvement of subgrade and/or base stiffness (i.e., resilient modulus) and (2) the improvement in tensile capacity of unbound materials. Several ongoing studies are currently in progress to establish the material properties of geosynthetic materials. A number of readily available test methods exist for the purpose of characterizing geosynthetics and their interactions with aggregate base materials. Geosynthetic-aggregate interface properties are most often measured using pullout methods or direct shear tests, which focus on the conditions at failure. However, such properties have not been adequately characterized for typical service conditions, resulting in relatively conservative empirical relationships. While a national guide of practice has not yet been established for geosynthetics, a number of AASHTO and ASTM methods exist and are generally used for this purpose, although the current AASHTO guidelines acknowledge that insufficient information is available at this time for a complete characterization. A 2007 FHWA publication includes guidance for the use of geosynthetics in roadways and pavements, and includes recommended minimum standards for the properties of ultimate multi-rib tensile strength and ultraviolet (UV) stability. While junction strength is also acknowledged as an important property, sufficient data was not available to recommend firm specifications. Additionally, minimum tensile modulus values were not included. The objective of this research is to develop a design methodology and guidelines on when, where, and how to use geosynthetic materials within a pavement structure. The guidelines will target design engineers and practitioners in the pavements and materials engineering community, with a focus on the most basic engineering properties of geosynthetics as they relate to structural pavement design. It is anticipated that the design principles contained in the guidelines could be readily incorporated into the Mechanistic-Empirical Pavement Design Guide (MEPDG). The initial task of this research effort will include a thorough review of available literature regarding geosynthetics, their laboratory-measured properties, and documented field performance. Because many "best practices" for the use of geosynthetics have been documented in previous research, the lessons learned from these efforts should be considered prior to developing the detailed laboratory work plan for characterizing geosynthetics. Additionally, a number of studies have demonstrated the field performance of geosynthetics; these findings should be incorporated into the scope of the work as appropriate, with additional field trials performed to validate the initial conclusions developed. A large portion of the work will revolve around the development of specific techniques for considering the effects of geosynthetics on the pavement performance prediction models contained in the MEPDG. The results of this research will provide a solid engineering basis for estimating the structural effects (benefits) of geosynthetics when properly placed within a pavement structure, effectively replacing the "rule of thumb" design procedures currently used. By more accurately characterizing the effects of geosynthetics, pavement structures may be constructed more efficiently while also providing a greater degree of design reliability. </font>

Language

  • English

Project

  • Status: Proposed
  • Funding: $600000.00
  • Contract Numbers:

    Project 1-50

  • Sponsor Organizations:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    Hanna, Amir

  • Start Date: 20100613
  • Expected Completion Date: 0
  • Actual Completion Date: 0
  • Source Data: RiP Project 26456

Subject/Index Terms

Filing Info

  • Accession Number: 01463931
  • Record Type: Research project
  • Source Agency: National Cooperative Highway Research Program
  • Contract Numbers: Project 1-50
  • Files: TRB, RiP, USDOT
  • Created Date: Jan 3 2013 2:33PM