Evaluation of Factors Affecting the Performance of Geogrid-Reinforced Granular Base Material Using Repeated Load Triaxial Tests

This research was performed to evaluate the benefits of geogrid reinforcement of granular base specimens and to study the effect of different factors contributing to their performance. This includes geometry, tensile modulus, and arrangement/location of geogrids, and the moisture content of specimen. Five geogrids of different tensile modulus and two aperture geometries (three rectangle or bi-axial and two triangle or tri-axial) were used. The study was experimentally carried out through conducting repeated load triaxial (RLT) tests to evaluate the permanent deformations of the specimens. The test results demonstrated the potential benefit in placing the geogrid within the granular base specimens. Less permanent deformations were measured under cyclic loading for geogrid reinforced base specimens compared to unreinforced specimens. The geogrid geometry and tensile modulus had noticeable effect on the specimens’ performance. Of the five geogrids used, the tri-axial geogrid (TX1) with triangle geometry and the highest tensile modulus, performed consistently better than the other four geogrids. For geogrids with the same geometry, the higher the tensile modulus, the lower was the accumulated permanent deformation. The test results also showed obvious effect of the geogrid arrangement/location on the specimens’ performance, with the double geogrid location consistently yielded the largest improvement. The effect of moisture content on the performance of geogrid reinforced specimens was evident, with higher improvement observed for specimens prepared at the optimum and dry of optimum than those prepared at wet of optimum.