Prediction of creep behaviour from load relaxation behaviour of polymer geogrids
Evaluation of creep behaviour of polymer geosynthetic reinforcement is important for predicting the long-term performance of geosynthetic-reinforced soil (GRS) structures and determining the creep reduction factor of geosynthetic reinforcement for the design lifetime of a GRS structure. The inherent link between the creep behaviour and the stress relaxation behaviour was confirmed by performing a comprehensive series of sustained loading (SL) tests and stress relaxation (SR) tests and numerical simulations of SL and SR tests on several geogrid types. In the framework of the non-linear three-component (NTC) model, the creep strain in SL is entirely irreversible, while the tensile load decrement in SR is associated with the developed positive irreversible strain with zero total strain rate. Measured systematic relationships between the elapsed times necessary to reach the same irreversible strain rate in SL and SR tests and those between the irreversible strain increments necessary to reach the same irreversible strain rate in SL and SR tests are presented and simulated by the NTC model. It is shown that, based on these relationships, the time history of creep strain can be predicted from given results of SR tests performed for a much shorter period. This method is validated by successful simulations of experimental results.