Study on a pullout behavior of two-layer soil-geocomposite under monotonic and cyclic loads

摘要

Apart from the monotonic loads, reinforced soil structures during their operation life can be subjected to seismic loads like road traffic, railways, or earthquakes. In this paper, to investigate the monotonic, cyclic, and post-cyclic pullout behavior of soil-geocomposite (Soil GPC 40/40) buried in two-layer soil (sand-geocomposite-gravel), a set of one-stage pullout (OSP) and multistage pullout (MSP) tests was conducted on a large scale. The effects of vertical stress, cyclic load frequency, cyclic load amplitude, and the number of cyclic loading cycles factors were evaluated on the monotonic and post-cyclic pullout two-layer soil-geocomposite. The results indicated that the vertical stress is effective for enhancing the monotonic pullout resistance, post-cyclic of two-layer soil-geocomposite, and has also a significant effect on the peak pullout resistance displacement. Comparing the results of MSP tests with the OSP tests results under the same conditions indicated that in all vertical stresses, cyclic loading reduced the post-cyclic pullout resistance in comparison with monotonic pullout resistance. Among the cyclic loading parameters investigated in the present study, the loading amplitude had the highest, while the number of loading cycle has the minimum effect on reducing the post-cyclic pullout resistance and increasing the cumulative cyclic displacements. As the two-layer soil-geocomposite sample under vertical stress of 60 kPa and A/P-rm = 0.5, due to the geocomposite fibers rupture, A 20.5 decline in resistance occurred compared to the monotonic pullout resistance. Also, the cyclic loading amplitude and vertical stress were the most important factors in altering the failure mode of the two-layer soil-geocomposite.