2ND SEVERN CROSSING - DESIGN AND CONSTRUCTION OF THE FOUNDATIONS

This paper describes the design and construction of the foundations fo r the second motorway bridge over the Severn estuary between England a nd Wales. The two main piers of the central cable-stayed bridge and th e 49 supports of the approach viaducts are founded mostly on exposed s andstone and mudrock. Owing to strong currents and the high tidal rang e, the contractor chose to construct 37 of the foundations using preca st caissons weighing up to 2000 t. These were floated out from the cas ting yard on the English shore and placed using specially adapted barg es. The remaining foundations were piled through alluvium or to span a n existing rail tunnel. All foundations were designed for potential sh ip impacts.