Investigation of geogrid base reinforcement mechanisms considering residual stress and confinement effects

Recent research at the University of Illinois focused on the development of a mechanistic model for the response analysis of geogrid reinforced flexible pavements. The model utilizes the finite element approach and properly considers the nonlinear, stress dependent pavement foundation as well as the isotropic and anisotropic behavior of the granular base/subbase materials. Compaction and preloading induced base course residual stresses can also be considered in the mechanistic analysis. The inclusion of geogrids in the granular base caused development of a stiffer layer associated with aggregate interlock around the geogrid reinforcement. The primary focus was to study increased confinement effects on improved layer moduli and reduced critical subgrade vertical strains/stresses, which contribute to geogrid tensile reinforcement mechanisms. An increase in horizontal confinement due to residual stresses resulted in significant increases in the moduli of the base and subgrade layers in the vicinity of the geogrid reinforcement. The degree of structural benefit provided by geogrid reinforcement could be successfully quantified in response analysis to show the commonly observed technical benefit of geogrids in the field.