In-Aggregate Performance of Unitized and Woven Geogrids in Open-Graded and Dense-Graded Aggregates

In-aggregate performances of unitized and woven geogrids in two types of gradations (i.e. open-graded and dense-graded) are compared in a laboratory study. A survey of geogrid products in the U.S. market and as specified for base reinforcement by all state departments of transportation was carried out prior to the selection of candidate geogrids for the study. The geogrids were classified according to their rib and junction strengths. This study focused on the influence of junction strength on the in-aggregate response of geogrids with comparable rib tensile strength and aperture size. The geogrids rib and junction strength values were determined from standard in-isolation tests. In-aggregate performances of the geogrids were examined using pullout tests in open-graded and dense-graded aggregates. The pullout test results in both types of aggregates indicated that significant difference in junction strength values of geogrids did not result in equally different pullout response under serviceability conditions. However, it was observed that unitized geogrids exhibited greater in-aggregate strength at higher strains that would represent heavier loads during the construction stage. Pullout resistances of both unitized and non-unitized geogrids were greater in the open-graded aggregate as compared to the dense-graded aggregate. On the other hand, the dense-graded aggregate showed lower displacements for its peak pullout resistance indicating a better serviceability performance.