An investigation into the performance of integral bridge abutment backfill under cyclic translational movements

Integral bridges without joints have proven to be effective in lowering the overall construction and maintenance cost compared to conventional bridges with expansion joints. However, there are uncertainties related to the design and analysis of integral bridges in response to cyclic thermal movements induced by deck expansion and contraction. The cyclic thermal movements of the abutments increase the lateral earth pressure on the abutment and its foundation, leading to soil settlement and heaving of the backfill soil. If there is no approach slab, the road surface elevation will be changed, and soil slumping will likely occur at the bridge's end. Although many design guidelines recommend using an approach slab to span over the void created by the settlement, with time and repeated traffic loading, the settlement trough will increase beneath the approach slab leading to structural failure of the approach slab. Furthermore, available design guidelines for integral bridges currently provide little or no information about the soil deformation behind the integral abutment under cyclic thermal loading. Therefore, the primary objective of this paper is to investigate the soil-abutment interaction at different magnitudes of cyclic translational movements and to study the settlement and heaving of the backfill. The experimental results show that the increase in the maximum settlement near the abutment increases with the increase in the magnitude of cyclic translational movements, but only up to a certain magnitude. Then the maximum settlement tends to reach a constant value with higher cyclic amplitudes. These findings will help to develop innovative and economical solutions to alleviate the soil ratcheting effect and to control the soil settlement and heaving behind abutment walls.