The traditional construction procedure of bridges involves the use of expansion joints to allow for unrestricted superstructure movements against the temperature induced deformations. However, expansion joints have been demonstrated to be vulnerable to deterioration thus requiring frequent and costly maintenance. In that regard, the Integral Abutment Bridge (IAB) system presents an attractive alternative to overcome such problems. In addition to the advantages achieved by eliminating the expansion joints, the IABs have desirable structural performance and offer simple and rapid construction procedures. In the last few decades, IABs have been increasingly utilised in many countries around the world. Nowadays, the integral and semi-integral abutment bridges are becoming the first choice in the construction of bridges. Nevertheless, the IABs yet have their unique problems that ensue from the regular expansions and contractions (including shrinkage) in the superstructure. These problems have negated some of the advantages of IABs and restricted their use. The complex soil-structure interaction mechanism in IABs has made it difficult for engineers to find the appropriate solution to address the approach issues in this type of bridges. Adopted remedy measures include the use of run-on concrete approach slabs, heavily compacted approach fill, compressible inclusion between the soil and the abutment, and self-stable MSE approach fill with gap separation between the abutment and the MSE fill. However, no single solution can adequately address the broad array of IAB cases, each under a different setting, across the world. The present thesis extends current insights on the soil-structure interaction of IABs, with particular emphasis on the effects on the soil settlement and the lateral pressure at the integral abutment approach. The aim is to provide a sound basis to develop potential or improve current mitigating solutions. The thesis then investigates using EPS geofoam as a mitigating solution through a study of soil-EPS and EPS–abutment interactions. A combination of physical modelling and numerical analyses has been utilized to perform these investigations. In the thesis, a comprehensive review of the existing practices in dealing with the soilstructure interaction effects in IABs has been undertaken. A novel analytical solution is developed to estimate the passive earth pressure based on an earlier hypothesis of Terzaghi. This solution provides an efficient tool to calculate the passive earth pressure which represents a fundamental input in the estimation of earth pressure in IABs
