CREEP AND STRESS-RELAXATION OF GEOGRIDS

Most research on the long term behavior of geosynthetics has focused o n creep; very little data is available on the stress relaxation behavi or of geogrids. Consideration of both creep and stress relaxation in d esign may ultimately produce a more efficient structure while allowing for the use of a smaller creep reduction factor. The results of an in itial effort to experimentally identify the stress relaxation behavior of nine typical geogrids used to reinforce soil structures is present ed. A simple test method that directly measures the stress relaxation of geogrids was developed. The geogrids were subject to initial loads of 40, 60, and 80% of their ultimate short term strengths. Each test w as carried out for a period of one month, or until creep rupture occur red, whichever was shortest. The maximum potential stress relaxation w as approximately 30% of the initial load for polyester geogrids, and 5 0% for polyethylene geogrids.