Long-Term Pullout Behavior of Polymeric Geogrids

Polymeric geogrids are widely used in various geotechnical-, transportation-, and environmental-related applications. Among the major uses of geogrids are reinforced soil walls, steep slopes, and landfill expansions. Current design practices are based on limit equilibrium techniques in which the geogrid is assumed to resist failure by mobilizing sufficient tensile resistance within the potential failure zone. The geogrid must also extend a sufficient distance beyond the potential failure surface to ensure sufficient anchorage resistance and thus resistance to pullout failure. This paper focuses on the anchorage behavior of geogrids under both short-term and sustained (1,000 h) conditions. An experimental investigation is conducted using five different geogrids in granular soil tested under two different normal stresses of 28 and 69 kPa. The geogrid length in all tests is taken equal to 0.9 m, which is often the requirement for the minimum anchorage length beyond the failure plane. Results of the tests are presented in terms of load-displacement curves and time-displacement curves. The results indicate that for practical purposes, the pullout strength after 1,000-h sustained loading can be assumed to be equal to the short-term pullout strength provided sufficient length of the geogrid is available to mobilize its full strength and/or the structural integrity of the geogrid is maintained during pullout over its length.