A mechanistic-empirical approach to quantify the influence of geogrid on the performance of flexible pavement structures

The objective of this study was to develop a methodology for quantifying the influence of geogrid on the performance of flexible pavement structures in a manner that would allow incorporation into Pavement Mechanistic-Empirical (ME) Design. The finite element technique was used to develop the geogrid-reinforced flexible pavement structure models, which focused on the characterization of the lateral confinement and vertical membrane effect of geogrid. A full-scale Soil Tank test was conducted to assess the validity of the developed geogrid-reinforced models by comparing the model predicted pavement responses (i.e., surface deflections, tensile strain at the bottom of asphalt concrete, and vertical stress distributions) to those tank test measurements. In general, the developed finite element models were capable of accurately predicting the responses of geogrid-reinforced and unreinforced pavement structures. It was found that the placement of geogrid increases the stiffness of base course and significantly reduces the vertical stresses around the geogrid layer, but cannot effectively reduce the tensile strain at the bottom of asphalt concrete. This indicated that the geogrid reinforcement is beneficial for reducing the rutting damage in base course and subgrade, but not effective in prolonging the fatigue life of flexible pavement. To quantify the influence of geogrid, the geogrid-reinforced flexible pavement structure was equivalent to an unreinforced flexible pavement structure with the modified material properties, which was based on a pavement response equivalency approach. The determined modified material properties was then input into Pavement ME Design software to predict the performance of geogrid-reinforced flexible pavement structures. Two case studies were conducted to predict the performance of two geogrid-reinforced pavement sections that were identified from the Long-Term Pavement Performance (LTPP) database. The predicted performance results (i.e., rutting depth and fatigue cracking area) were coincident with those field measurements, which validated the prediction accuracy of the proposed approach.