Performance of a triaxial geogrid-reinforced crushed rock base underlain by a soft clay subgrade

This large-scale test investigated the behavior of a pavement structure composed of a crushed
rock base underlain by a soft clay subgrade reinforced with a triaxial geogrid under static loading.
The fully instrumented pavement model included a 0.8-m-thick soft clay layer and a 0.2-m-thick
crushed rock layer. A triaxial geogrid, Triax TX150, was installed at the interface between the
subgrade and base layers and the mid-depth of the crushed rock base. Both unreinforced and
reinforced pavement models were prepared in a square steel mold of 1.5 m width and 1.2 m
height. Plate load tests were conducted according to ASTM standards. The results revealed that
the number of geogrid layers and their locations influenced the reinforced pavement’s ultimate
bearing capacity and failure mechanisms. Two-layer reinforcement (between the crushed rock
and soft clay layers and in the middle of the crushed rock layer) provided the maximum bearing
capacity, with an improvement factor of 1.63 compared to that of the unreinforced pavement,
because the triaxial geogrids changed the failure mode of the unreinforced pavement from
punching failure in the crushed rock and local shear failure in the soft clay to only punching
failure in the crushed rock. Thus, triaxial geogrids are suggested for enhancing the performance of
pavements on soft clay subgrades.