Large-scale pullout testing and numerical evaluation of U-shape polymeric straps

In this paper, U-shape polymeric strap (UPS) reinforcement, which can develop passive resistance in the soil, is investigated. The curved (looped) part of the strap at the free end of the reinforcement generates a passive resistance in the soil and increases the pullout resistance beyond what is available due to friction of the horizontal portions of the strap. In this paper, UPS pullout resistance is first compared with that of the typical double polymeric strap (DPS) through large-scale pullout experiments. The experimental results in compacted granular soil show that the curved strap part of the DPS configuration is capable of increasing the pullout resistance by about 130–194%. To improve understanding of pullout behavior, 3D finite element modeling was used to model the pullout behavior of the DPS and UPS configurations. In addition, the bearing resistance factor (Nq) was calculated using three equations for general shear failure, punching shear failure and ‘hybrid’ failure. The equation for general shear failure gave the best agreement with measured values of Nq from the laboratory pullout tests.