Deformation mechanisms of semi-integral bridge abutments in dry and saturated soil

Semi-integral abutment bridges are becoming increasingly popular worldwide. Eliminating expansion joints along the semi-integral bridge slab has considerably reduced maintenance costs. Many of these bridge abutments were designed and constructed on loose, dry sand with a deep groundwater level. However, climatic change hazards, such as floods, have raised awareness of the resilience of these abutments under earthquake loading following a rise in the water table level. Consequently, a series of centrifuge tests have been conducted to understand the backfill-abutment interaction under earthquake loading. This paper presents the results of two centrifuge experiments to show the deformation mechanisms of a bridge abutment constructed on dry and saturated foundation soil. The centrifuge results reveal that a moderate earthquake is enough to liquify the loose sandy soil under the abutment, eventually leading to severe abutment rotation of around 2.5° and a residual abutment movement more than ten times higher than the design limit recommended by the EC8 – Part 2. Further, the structural loading and response have also increased considerably. The abutment flexural bending and the deck axial force are nearly double those when the abutment is constructed on dry soil. Simplified deformation mechanisms for the backfill-abutment system under earthquake loading are proposed, allowing bridge engineers to better account for the effects of climate change and multi-hazard events during the design stage.