BRIDGE PIER SCOUR ASSESSMENT FOR THE CONFEDERATION BRIDGE

The Northumberland Strait Crossing Project has presented many engineer ing challenges, one of which has been the assessment of scour protecti on requirements for the 65 bridge piers. The direct application of sta ndard scour design techniques was not possible for this project becaus e of the combination of complex flow conditions (waves and currents), complex pier geometry (conical pier bases, with some piers located in dredged pits), and complex seabed conditions (highly weathered and fra ctured bedrock). A multi-faceted coastal engineering investigation was undertaken by Baird & Associates to assess the scour protection requi rements. Key activities included geotechnical investigations to define the seabed characteristics, numerical modelling to define the wave, c urrent, and water level conditions at thr crossing site, physical mode lling of wave-current interaction with the bridge piers, and the devel opment of a new methodology to estimate the erosion potential of the s eabed around the bridge piers under extreme wave and current condition s. This technical note provides a brief overview of the investigations completed and a description of the new scour design methodology.