Effects of Backfill Constitutive Behavior and Soil–Geotextile Interface Properties on Deformations of Geosynthetic-Reinforced Soil Piers under Static Axial Loading

Abstract

In this research, a numerical investigation was conducted to study the effects of backfill constitutive behavior on the vertical and horizontal deformations of geosynthetic-reinforced soil (GRS) piers under static axial loads. A finite-difference program was used to model full-scale GRS piers. The backfill soil was simulated using three constitutive models: the elastic-perfectly-plastic Mohr-Coulomb model, the plastic-hardening model, and the plastic-hardening model combined with strain-softening behavior. The results showed that the deformation response of GRS piers under service loads is satisfactorily predicted by the plastic-hardening model. At ultimate failure loads, however, only the model accounting for the plastic-hardening and the strain-softening behaviors was judged to reasonably capture the behavior of GRS piers. The relative displacement of soil and geotextile at the soil–geotextile interface was also investigated. The results showed that under working conditions with small applied load, there is no sliding between the soil and geotextile; however, as the load increases, sliding is first initiated at the corners of the pier and progressively mobilized toward the center of the pier. A parametric study on the effects of soil–geotextile interface properties on the deformation behavior of GRS piers under axial loading was also conducted using the validated plastic-hardening model combined with strain-softening behavior. It was found that increasing the interface friction angle decreases the settlement of GRS piers when the axial strain is greater than 2% for piers with a concrete masonry unit (CMU) facing and 4% for piers without CMU facing. The results suggest that when calibrating the interface friction angle (or cohesion), the postyielding response of GRS pier should be used.