Validated Mechanistic Model for Geogrid Base Reinforced Flexible Pavements

A mechanistic response model was recently developed at the University of Illinois to analyze geogrid base reinforced flexible pavements designed for low to moderate traffic volumes with a relatively thin hot-mix asphalt surface layer. This model utilizes the finite element approach and properly considers (1) the nonlinear, stress-dependent behavior of pavement foundation geomaterials, i.e., unbound aggregates and fine-grained soils; (2) anisotropic behavior of the granular base layer; and (3) the compaction and preloading induced unbound aggregate base residual stresses. To validate the developed mechanistic model, field response data were collected from instrumented full-scale pavements constructed with both geogrid reinforced and control test sections. The model predictions using the nonlinear and anisotropic characterizations of the granular base layer moduli were found to better capture the magnitudes and the trends in the measured response data. After trafficking to failure of the pavement test sections, pavement trench studies were conducted to gather constructed layer thicknesses and additional forensic data in an effort to provide refined inputs for the mechanistic response model. An increase in stiffness observed around the geogrid reinforcement in the field was properly modeled by the use of horizontal residual stresses above the geogrid, which resulted in a better match of the predicted with the measured pavement responses of the reinforced sections. As a result, the mechanistic model predictions computed at different locations in the test sections compared reasonably well with a large number of field measured responses under different load levels.