The report presents a literature review of the behaviour of integral bridge abutments and the effects on the surrounding ground. Based on this review there is evidence to indicate that cyclic thermal movement of an integral bridge abutment results in an increase in earth pressure up to the limiting value K(sub p) acting behind the abutment wall. The pressure depends on the magnitude of the induced soil shear strain resulting from wall movement towards the backfill or retained soil together with the number of movement cycles. The rate of increase of pressure would appear to be dependent on the magnitude of the shear strain which is dependent on the bridge span subjected to thermal movement and the abutment height. Typically earth pressures may take 5 to 10 years or more of seasonal cyclic movement to reach the limiting value K(sub p). Cyclic thermal movement of an integral abutment may also affect the general stability of the foundations and underlying soils, particularly spread footings. Horizontal sliding of shallow spread footings may occur, if insufficient restraint is provided by the abutment backfill or retained soil, and this could result in elasto-plastic soil behaviour beneath the foundation leading to unacceptable settlement or ground instability. In practice, however, many hundreds of integral bridge abutments have been constructed in Europe and North America with little or no sign of structural distress. The possible reason for the satisfactory performance of these bridges is that they have relatively moderate spans and the induced shear strains behind the abutments are such that any increase in pressure can be redistributed in the structure and surrounding soil. Longer span bridges, in which the induced shear strains are potentially large are unlikely to be able to allow redistribution of the associated higher pressures. Increase in earth pressures above the design value and up to the limiting pressure value K(sub p) could then occur, together with foundation movement, resulting in structural distress. Tentative guidance on the likely magnitude of induced soil strain, soil behaviour and parameters to be used for the design of an integral bridge abutment are presented in this report. (A)

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