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Development of Design Methods for Geosynthetic Reinforced Flexible Pavements

Project #: 426202
Start Date: 09/01/2001
End Date: 03/30/2004
Status: Completed

The 2002 Pavement Design Guide currently under development through NCHRP Project 1-37A, and similar mechanistic-empirical (M-E) methods under development in Europe, will provide significant advances in terms of a designer’s ability to increase pavement design reliability, particularly when non-traditional pavement loads, geometries or materials are used. This guide, as well as those in Europe, is not, however, capable of addressing structural benefits offered by the addition of a reinforcement layer, such as a geosynthetic or steel mesh. This project will provide methods for incorporation of reinforcement products in flexible pavements for structural support of the pavement system, where these methods will be compatible with the 2002 Pavement Design Guide. The sponsors for the project include the Federal Highway Administration, the Norwegian Research Council, the Finnish, Norwegian and Swedish road agencies and several reinforcement manufacturers. The project is being conducted by a team of researchers consisting of the Western Transportation Institute at Montana State University, SINTEF Civil and Environmental Engineering, Trondheim, Norway, University of Maryland and Christopher Consultants. M-E methods contain three basic components where reinforcement features will be introduced. Reinforcement will be added as a structural component to the finite element response model along with material models describing the reinforcement and reinforcement-aggregate shear interaction. The next component is the material model for the unbound materials. Various material models having the potential to illustrate effects from the reinforcement will be examined. The third component lies in the damage models used for pavement rutting and pavement fatigue. Reinforcement effects from the first two components influence pavement life as determined through the damage models. The project involves the testing of asphalt concrete, base aggregate and subgrade materials used in test sections previously constructed in two different facilities. These tests will define basic material properties for use in the material characterization models. In addition, large-scale cyclic triaxial tests will be performed on reinforced aggregate specimens to assess changes in parameters contained in unbound material models and in the damage model for rutting model for rutting. Parameters from these tests will be compared to those from conventional tests on unreinforced aggregate to assess how reinforcement changes fundamental material properties. Several types of material tests are being performed on geosynthetics to provide properties for the geosynthetic and shear interaction properties between the geosynthetic and surrounding unbound materials. The tests are designed for conditions appropriate to this application, including small levels of strain and shear displacement, confinement and cyclic loading. In addition to the research tasks described earlier, a number of activities are planned to provide for implementation of the results of the project. Implementation action plans will be developed with the AASHTO Joint Task Force on Pavements and with the AASHTO Committee on Materials. Liaison with the Geosynthetics Materials Association will provide for acceptance by members of industry. Members of the project will participate in the European COST action on Reinforcement of Pavements with Steel Meshes and Geosynthetics to share information and benefit from activities within Europe. Finally, procedures for future addenda to the 2002 Pavement Design Guide will be identified such that steps can be made to implement project findings into the 2002 Guide.


The project will develop mechanistic-empirical design methods compatible with the 2002 Pavement Design Guide for flexible pavements structurally reinforced with geosynthetics and steel meshes.