Absence of deck expansion joints in integral abutment bridges (IABs) offers multiple benefits that encompass increased redundancy, enhanced resilience, and diminished construction and lifetime maintenance costs. IAB's deck and girders undergo cyclic seasonal expansions and contractions accompanied with abutment translation and rotation that results in a near surface granular backfill collapse and creation of a void behind the abutmtment. The resulting loss of soil support leads to approach slab distress and severe approach slab settlement that often occurs shortly after the completion of construction.
This research evaluates the effectiveness of a compressible wedge shaped inclusion, placed directly behind the IAB abutment, in alleviating the bridge approach settlement. This is accomplished by testing a downscaled physical model of the actual integral bridge abutment, piles and backfill. The abutment is subjected to 100 cycles of forward-backward displacement simulating cyclic seasonal superstructure expansion and contraction that occurs during 100 years of a bridge life cycle due to ambient temperature changes. Digital imaging correlation (DIC), a technique described as a non-contact optical deformation measurement, was used to capture the evolution of backfill displacements and strains. These mechanisms elucidate development of backfill failure and collapse mechanisms that are ultimately responsible for bridge approach settlement in IABs. Based on the results of DIC analysis and other measurements it was found that compressible inclusions favorably modify deformation mechanism in the backfill soil behind the expanded polystyrene (EPS) geofoam inclusion resulting in two times smaller settlement than in the case without and inclusions or reinforcements.

bridge approach settlement; digital imaging; integral bridges; near surface soil collapse