Evaluation of the Base/Subgrade Soil under Repeated Loading : Phase I \u2013 Laboratory Testing and Numerical Modeling of Geogrid Reinforced Bases in Flexible Pavement

6821606502009Interim report; Aug. 2003-May 2007.PDFTech ReportFHWA/LA.09/450Subgrade (Pavements)Base course (Pavements)Flexible pavementsDeformationGeogridsPavements--SubgradesPavements, FlexibleSurfaces, Deformation ofDeformations (Mechanics)GeogridsLouisianaLouisiana Transportation Research CenterAbu-Farsakh, MuradNazzal, MunirLouisiana State University (Baton Rouge, La.). Department of Civil and Environmental EngineeringNTL-HIGHWAY/ROAD TRANSPORTATION-MaterialsNTL-HIGHWAY/ROAD TRANSPORTATION-Soils and GeologyUS Transportation CollectionThis report documents the results of a study that was conducted to characterize the behavior of geogrid reinforced basecourse materials. The research was conducted through an experimental testing and numerical modeling programs. Theexperimental testing program included performing different laboratory tests to evaluate the effect of various factors on theperformance geogrid reinforced base course materials. Finite element models were also developed to investigate thebenefits of placing geogrids within the base course layer in a flexible pavement structure. The results of the experimentaltesting demonstrated that the inclusion of the geogrid reinforcement layer(s) improved the compressive strength andstiffness of base course materials under static loading. This improvement was more pronounced at higher strain levels.Furthermore, the results showed that the geogrid significantly reduced the base course material permanent deformationunder cyclic loading, but it did not show appreciable effect on their resilient deformation. The finite modeling programshowed that the geogrid reinforcement reduced the lateral, vertical, and shear strains within the base course and subgradelayers. Furthermore, the geogrid had an appreciable reduction in permanent deformation for pavement sections built ontop of weak subgrade soils with medium to thin base layer thickness, with the thin base layer thickness showing greatervalues of improvement. However, negligible to modest reinforcement effect on permanent deformation was obtained forsections having a firm subgrade or thick base layer thickness. The geogrid reinforcement had modest to high values ofimprovement in fatigue life of pavement structure.90