CONFEDERATION BRIDGE - NEW SCOUR DESIGN METHODOLOGY FOR COMPLEX MATERIALS

The $800 million Confederation Bridge, spanning 13 km across the Northumberland Strait in Eastern Canada, presented many engineering challenges, one of which was the assessment of scour potential and protection requirements for the 65 bridge piers. The direct application of standard scour assessment/design techniques was not possible for this project due to the combination of complex flow conditions (waves and currents), complex pier geometries (conical pier bases, with some piers located in dredged pits), and complex seabed conditions (highly weathered and fractured bedrock). A multi-faceted coastal engineering investigation was undertaken by Baird & Associates to assess scour potential, define scour protection requirements and design scour protection. Key activities included geotechnical investigations to define the seabed characteristics; numerical modeling to define the wave, current and water level conditions at the crossing site; physical modeling of wave-current interaction with the bridge piers; the development of a new methodology to estimate the scour potential of the seabed around the bridge piers under extreme wave and current conditions; and post-construction scour monitoring. This paper provides an overview of the investigations completed, including a description of the new scour design methodology and the results of the scour monitoring program over the five year period since the bridge was completed.