The increasing use of polymeric geogrids in reinforced soil structures requires a better understanding of soil-geogrid interaction.  Pullout tests are commonly used, but most of them have been short-term tests using granular soils.  Very little research has been reported on the behavior of geogrids under confined by clay and subjected to both static and dynamic loads.

        This research focuses on the long-term pullout behavior of a geogrid embedded in clay and subjected to sustained and repeated tensile loads under unconfined and confined conditions.  A polypropylene geogrid embedded in kaolinite was used.  For repeated loading tests, incremental tensile loads of different frequencies and amplitudes were applied to the geogrid using an existing testing fixture.  Strain gauges were used to monitor the local strain along the length of the geogrid specimen.

        Creep developed in the geogrid as the applied tensile load increased.  The creep strain rate of the geogrid was found to be a function of load amplitude.  However, the frequency (0.1 Hz and 0.5 Hz) of applied load did not show a significant influence on creep strain.  Creep under repeated load was smaller than that under sustained load.  The confining material and pressure intensity have important effects on both creep and strain distribution along the embedded grid.  This study provides baseline information for future research and development on quantifying the interaction behavior between geosynthetics and cohesive soils.