Effect of Clayey Fine Content on Cyclic Deformative Pullout Behavior of PET Geogrid Embedded in Pure Sand

Several monotonic and multistage pullout tests were conducted by means of a large pullout device to investigate the effect of cyclic loading on the peak post-cyclic pullout interaction coefficient and deformative behavior of uniaxial polyester geogrid tested in pure sand and sand including 10% or 20% clay. An experimental approach was employed to study the influence of the cyclic load amplitude and frequency, number of load cycles, and normal stress on the displacement of a geogrid during the cyclic stage. The results showed that, at a normal stress of 20 kPa, the applied load amplitude caused a reduction in the post-cyclic peak pullout interaction coefficient of the geogrid when compared to similar monotonic pullout tests. The head displacement of the geogrid increased as the normal stress and load amplitude increased at normal stresses of 20, 40, and 60 kPa. However, an increase in the frequency of the load decreased head displacement of the geogrid in pure sand and 20% clayey sand at a normal stress of 40 kPa. Under similar applied load amplitudes, the head displacement of 20% clayey sand was lower than those measured in pure sand due to the higher placement density. Increasing the number of load cycles from 30 to 100 slowed the rate of increase in head displacement, indicating the existence of a stable soil–geogrid interface.