Centrifuge modelling of EPS geofoam behind integral bridge abutments

This research investigates the extent to which geosynthetic compressible inclusions can be used to improve the performance of integral bridges. Geotechnical centrifuge modelling was used to simulate thermal movements acting on a 9 m abutment on a spread foundation, with and without a 1.2 m thick EPS geofoam inclusion. The compressible inclusion was found to significantly reduce the earth pressures behind the abutment generated over a 120-year design life of thermal cycles without undergoing notable permanent deformation. This resulted in the bridge deck axial force and peak abutment bending moment reaching only a third and two-thirds, respectively, of the values without the geofoam. Backfill settlement increased slightly when the compressible inclusion was used, although the peak settlement immediately behind the abutment face remained similar at around 100 mm. Through the application of extreme displacement amplitudes, it was found that the performance of EPS geofoam was not overly sensitive to permanent deformation, which was concentrated behind the top half of the abutment. By providing partial isolation, rather than accommodating thermal movements in their entirety, these results suggest that EPS geofoam can improve integral bridge performance even when subjected to large thermal movements.