Bridges

Cover of Cape Preston Creek Bridge Over Environmentally Sensitive Tidal Mudflats
Cape Preston Creek Bridge Over Environmentally Sensitive Tidal Mudflats
  • Publication no: ABC-DES803-14
  • Published: 22 October 2014
The Sino Iron Project is located approximately 100 km south-west of Karratha at Cape Preston, WA. The access route from the mine site to the port has to provide for the delivery of heavy over-sized loads of up to 2000 tonne GVM. A key infrastructure component is the 2000 m long causeway and bridge over the soft tidal mudflats and creek between Cape Preston and the mainland.The causeway over the mudflats comprises a geotextile reinforced crushed rockfill floating embankment with flexible precast concrete slope protection against storm surges and wave action. To meet the tidal flow requirements, an additional seven flexible pipe arch culverts were provided along the causeway. The bridge layout was determined by considering the soil-structure interaction of predicted ground movements arising from the causeway embankment on the relatively thick, very soft mudflat soils next to the creek. The bridge was designed to restrain the inherently unstable approach embankments at the abutments, and the forces and displacements generated in the bridge structure were assessed from detailed 3D FE soil-structure interaction analyses.The bridge comprises a multiple-piled jetty type structure constructed from an elevated travelling piling platform. The design, materials procurement and construction of prefabricated steel tube piles, steel box headstocks and precast concrete planks enabled the contractor to meet the accelerated delivery program of seven months. This paper describes the challenges encountered during the design and construction of this major infrastructure, and presents the solutions and innovations adopted to deliver the works under difficult environmental, geotechnical and access conditions.