Full-height piled bridge abutments constructed on soft clay

Full-height piled bridge abutments constructed on soft clay are prone to lateral soil–structure interaction effects resulting from placement of the retained fill, and associated deformation of the underlying soil. The interaction increases lateral structural loading and displacement, and hence may result in unserviceable behaviour of the abutment or bridge deck. A series of geotechnical centrifuge tests and finite element method analyses are reported, examining the effect of clay layer depth and the rate of embankment construction. Agreement of data from the two methods is good, and the results confirm the existence of established lateral soil–pile interaction in the clay layer. However, additional interaction effects associated with the retained embankment material were also identified, causing a significant additional component of lateral loading on the structure. Such interaction increases bending moments in the piles, which are therefore of concern. Many existing empirical methods attempt to estimate these moments directly. However, it is argued that the moment loading is most logically viewed as a consequence of the lateral loading components acting on the pile, and that a simple calculation based on this information is likely to be considerably more reliable.