Application of advanced soil constitutive models to investigate complex soil-structure interaction issues in integral abutment bridges

The jointless design of integral bridges transfer deck expansions and contractions from ambient temperature fluctuations directly to the abutments. This cyclic behaviour leads to approach settlements and increases lateral earth pressures on the abutment. While numerical methods have been used to investigate this complex backfill-abutment interaction, most studies have relied on perfectly-plastic constitutive models for soils or have only validated passive pressure development over a limited number of cycles, neglecting settlement. Hence, previous research on numerical techniques have been unable to capture realistic service conditions, where integral abutments endure hundreds of cycles leading to densification and significant subsidence in the approach. This paper investigates the performance of three sophisticated constitutive models against the widely used Mohr-Coulomb (MC) model for simulating the backfill: SANISAND with Memory Surface and Semifluidized State (S-MSf), Hypoplasticity with Intergranular Strain (Hypo-IS) and Hypoplasticity with Intergranular Strain Anisotropy (Hypo-ISA). The backfill-abutment interaction is simulated using the Mohr-Coulomb friction (MCF) and Hypoplasticity with Intergranular Strain friction (Hypo-ISF) models. These models are carefully evaluated on simulations of centrifuge tests for integral abutments with different backfill relative densities, abutment heights and cyclic amplitudes. Results indicate that the MC and Hypo-IS constitutive models cannot capture the long-term backfill response. While integrated with the MCF contact, both S-MSf and Hypo-ISA deviated from experiments. The Hypo-ISA and Hypo-ISF pair estimated well the passive pressure development for the cases involving very large and very small abutment displacements. S-MSf demonstrated the best overall agreement with centrifuge data when paired with Hypo-ISF.