Prediction of long-term creep behavior of an HDPE geogrid by accelerated stress relaxation techniques

Accurately understanding the creep behavior of polymer geosynthetic reinforcements is key to designing durable geosynthetic-reinforced soil (GRS) structures. Establishing the creep reduction factor (RFCR) for a specific design life has traditionally required extended conventional creep testing to produce a creep rupture curve. To expedite this process, temperature-acceleration techniques, such as the conventional time-temperature superposition (TTS) and the stepped isothermal method (SIM), have been adopted to accelerate creep deformation. Since the material’s viscous properties influence both creep and stress relaxation, stress relaxation occurs at a faster rate than creep for the same irreversible strain under a given load. A framework has been empirically developed to relate the time history of stress relaxation to creep strain, allowing for effective prediction of long-term creep strain using short-term stress relaxation data. This study applies temperature-acceleration methods to short-term creep and stress relaxation tests on a high-density polyethylene (HDPE) geogrid. Results provide extended time histories for creep strain and stress relaxation, with durations extended by a factor of 250. By establishing a relationship between these time histories, a comprehensive method to predict long-term creep behavior is developed, combining the time factors of both methods to produce an approximately 1,635-fold extension. This streamlined approach enables an efficient and reliable prediction of HDPE geogrid creep behavior over long durations.