Large-Scale Plate Load Tests of Geogrid-Stabilized Aggregate Layers over Weak Clayey Subgrade

Abstract Geogrid-stabilized aggregate layers are used to increase the bearing capacity of weak subgrade material. Applications of these geogrid-aggregate composite layers include, but are not limited to, temporary working platforms, road construction, and railway ballast. The interaction of the geogrid with the aggregate creates a stiffer, stronger composite material that has properties that cannot be predicted from the results of soil testing or in-air index testing of geosynthetic properties. Given the challenges associated with scaling, centrifuge or other simulation is not realistic, and thus full-scale physical modeling is required. This paper presents details of what we believe to be the largest-ever full-scale controlled plate load tests, which were carried out near Clavet, SK, Canada. A 1 m square plate was used to load both geogrid-stabilized and nonstabilized aggregate test pads constructed over a relatively weak silty clay. This system, with a maximum load capacity of 1,060 kN, brought each pad to and past its ultimate bearing capacity, with load and displacement measured directly. Analyses, including cone penetration testing, photogrammetry, and intensive material characterization, were done before and after plate load testing. Results showed that the stabilized layers outperformed the nonstabilized layers. The stabilized layers demonstrated more consistent results between tests, averaged higher ultimate bearing capacities, had prolonged peak loads, and had improved values of modulus of subgrade reaction. Follow-up publications will have further analysis to quantify the benefits provided by stabilized layers as well as to explore the failure mechanisms with and without geogrid.