A review of soil deformation and lateral pressure ratcheting phenomena in integral abutment bridges

Integral bridges have been proposed as a jointless design alternative to the traditional counterparts, possessing copious potential economic and structural advantages. However, due to the monolithic connection at the girder-abutment interface, longitudinal deformations from the superstructure must now be accommodated by the stiffness of the approach backfill and soil surrounding the foundation. Consequently, in addition to traffic loads, integral bridge approaches are subjected to long-term, cyclic loading due to diurnal and seasonal thermal variations. This has resulted in two progressive geotechnical phenomena: an escalation of lateral passive pressures at the abutment-soil interface and accumulated deformations near the bridge approach. Over the last two decades, several investigations on the approach backfill-abutment interaction have been carried out. However, previous reviews on integral bridges have not comprehensively discussed the theoretical aspects of these two complex geotechnical issues. Hence, this paper presents a discussion on the long-term response of stress ratcheting observed from controlled analyses, along with a comparison to that from field monitoring data. Subsequently, the occurrence of accumulated deformations, along with a correlation to the mechanism of the cyclic interaction is explored. The effects of foundation design choice and skew angle on the passive pressure accumulation and soil deformation behavior are then presented. Subsequently, approaches used to mitigate the effects of the backfill-abutment interaction are compared. From this review, it is apparent that outcomes based on available experimental and field investigations are yet inadequate to develop analytical models required to predict the long-term response of integral bridge approach backfills under various loading conditions.