5. Conclusion
Based on the test results of the cyclic plate load testing program
on pavement test sections with and without geosynthetic reinforcement
inclusion, the following conclusions can be drawn:
1. The test results demonstrate that both geosynthetic products
significantly improved the performance of the pavement section
in terms of reducing the surface permanent deformation and
extending the service life of pavement sections. With a single
layer of geosynthetic placed at the baseesubgrade interface, the
adjusted traffic benefit ratio (TBRadj) can be increased up to
1.52 at a rut depth of 19.1 mm for pavement constructed using
457 mm (18 in.) thick base layer on top of weak subgrade soil.
2. The inclusion of geosynthetic reinforcement results in redistributing
the applied load to a wider area, thus reducing the
stress concentration and achieving an improved vertical stress
distribution on top of subgrade layer. This behavior results in
less accumulated permanent deformation in the subgrade, i.e.,
lower maximum vertical stress on subgrade, and hence the
lower permanent vertical strain in subgrade.
3. Among all six pavement sections tested in this study, the best
performance was observed for the pavement section with
double geosynthetic reinforcement layers. However, one also
should keep it in mind that the cost of having two layers of
reinforcement is higher than a single layer of reinforcement.
4. The instrumentation measurements indicate that geosynthetics
placed at the baseesubgrade interface function more as stabilization
of weak subgrade soil than as base aggregate reinforcement.
By placing an additional geogrid layer at the upper
one-third of the base layer, the permanent deformation in
base layer can be significantly reduced.