Investigating the Performance of Geogrid Reinforced Unbound Layer Using Light Weight Deflectometer (LWD)

This study investigates the performance of geogrid-reinforced unbound pavement layer. In this study, geogrid was used in various layouts and numbers using three different gradation of granular materials. Light weight deflectometer (LWD) device is known as a useful tool to evaluate the stiffness of unbound pavement layers. In this study, the LWD was utilized to experimentally investigate factors affecting the performance of geogrid reinforcement, including the number of geogrids, geogrid layout, and the gradation of unbound layer. There are several parameters which affect the LWD test results including the hammer weight, the falling height, and the surface stress. The effect of these parameters was also investigated. The results indicated that the improving effect of geogrid reinforcement is highly dependent upon the gradation of unbound layer. Incorporation of geogrid on the well-graded unbound layer decreased the elastic modulus; while, improving effect of geogrid reinforcement was observed on coarse and gap-graded unbound layers. It was also shown that geogrid reinforcement shows the best performance when one geogrid layer is installed at the bottom half of the unbound layer. The results of the LWD test showed that the LWD measurement at a particular hammer weight and falling height could be calibrated to a standard setting using the hammer's gravitational energy concept.