A review of progressive soil deformation occurring in integral bridge approaches

Integral bridges are a relatively recent design concept in which there is structural continuity at the girder-abutment interface. Whilst this has led to numerous advantages, it has also resulted in performance complications. Amongst numerous drawbacks, cyclic deformations of the bridge deck due to daily and seasonal temperature changes result in two notable geotechnical issues: ratcheting of passive lateral pressures on the abutment wall and progressive soil deformation in the approaches. During the last two decades, considerable research efforts have been dedicated to developing an understanding of these phenomena. However, it is apparent that a majority of the attention has been focused on stress ratcheting. Further, there is not yet a review available that assesses the theoretical aspects of soil deformation in integral bridge approaches. Accordingly, this manuscript presents a critical review of the long-term behaviour of soil subsidence and upheaval observed from controlled analyses. Subsequently, the impact of design parameters, namely, bridge length and foundation design are discussed. The significance of diurnal cycles on soil deformation is then presented. Through this review, it is understood that the formation of the settlement trough can reach a limiting state. However, due to the sustained accumulation of plastic shear strains, upheaving may continue to propagate, even in subsequent cycles. Soil upheaval is particularly influenced by the abutment movement mode and daily thermal fluctuations. Collectively, data from available literature is yet insufficient to predict the long-term soil deformation response of integral bridges.