Characterization of the Long-Term Tensile Stiffness of Geogrids at the Serviceability Limit of Strain

The characterization of long-term tensile stiffness of geogrids is required for various geotechnical applications, such as the design of geosynthetic-reinforced load transfer platforms within column-supported embankments. While ultimate creep strain information is generally included in manufacturer-provided product data sheets, current recommendations for the estimation of the long-term tensile stiffness of geogrids at the serviceability limit of strain require interpretation of isochronous curves not readily available to practitioners. Therefore, reduction factors generated for ultimate creep strain failure are often used for serviceability loading conditions, a method which has not been validated. This paper presents a method for appropriately scaling available ultimate creep strain information to obtain reduction factors for the serviceability limit creep strain. For a variety of geogrids, reduction factors estimated using the proposed method and direct use of the reduction factor at rupture are compared to reduction factors generated with interpreted values from isochronous curves. Results of the proposed scaling framework show good agreement with factors from the interpretation of isochronous curves; additionally, results suggest that the direct use of the reduction factor at rupture may be acceptable.