Myth and Fact on Long-Term Creep of GRS Structures

The long-term design strength of a geosynthetic reinforcement employed in current design methods is determined either by performing laboratory tests on the geosynthetic without considering soil-geosynthetic interaction or by imposing a very large safety factor to the tensile strength of the geosynthetic without any regard to the effect of backfill. This paper reviews long-term creep behavior of soil-geosynthetic systems and proposed revisions to the current design methods. Based on the authors' experiences and judgments, a cumulative long-term reduction factor, k, for geosynthetic reinforcement is recommended. The value of k is a function of the backfill gradation and index properties, reinforcement spacing, and geosynthetic polymer type. In addition, a rational procedure to account for soil-geosynthetic interactive creep behavior based on the SGIP test is presented.