Behavior of integral abutment bridges using geosynthetics under temperature variations

Expansion and contraction of bridge girders due to seasonal temperature changes force the integral bridge abutment to move toward and away from the backfill, which can lead to excessive backfill settlements and high lateral earth pressures behind the abutment. To solve these problems, Expanded Polystyrene (EPS) geofoam and geogrids were used as countermeasures to evaluate their mitigation effects through a series of model tests. A total of 100 lateral cycles were applied at the top of the abutment wall to simulate the long-term cyclic movement of bridge girders under seasonal temperature variations. The results showed that the EPS geofoam could effectively reduce the backfill settlement immediately behind the abutment wall by 55% and the lateral soil thrust by 51% compared to the abutment model with no mitigation, owing to the high compressibility of geofoam, which accommodates compressive deformations and mobilizes more soil shear strength. Geogrids could significantly reduce settlement but show a moderate effect in reducing lateral soil thrust, as the geogrid reinforcements restrict the deformation of backfill soils, resulting in less shear strength being mobilized. The combination of EPS geofoam and geogrids notably reduces both settlements and lateral earth pressures, with the EPS geofoam playing a more dominant role.