Corrosion

A key feature of the award-winning State Theatre Centre in Northbridge was the requirement for greater than 100 years of structural durability – ideally serving the WA theatre community and enthusiasts well beyond the century mark. Perth, and Northbridge in particular, are built on reclaimed swampland between the river, and what is now Lake Monger. The lower half of this structure is permanently submerged in this aquatic environment – sometimes up to 8 metres below the water table. During the course of the geotechnical testing it became clear that there were also pockets of acid sulphate soils in these clays at a 3.5m depth.

Sulfate ions tend to accumulate in coastal clays whenever ocean waters flood into an estuary. Such soils can react to form sulphuric acid if exposed to air, causing not only acidity and leaching of metals, but also a potential corrosion threat to building materials. Disturbing the soils can result in corrosion in surrounding buildings in addition to the environmental impact.

To contain all dewatering activities to within the boundary, diaphragm walls were erected to a designed depth to form a box, inside which, the water table levels could be controlled. The use of top-down construction and diaphragm walls eliminated the need for corrosion-susceptible permanent ground anchors to support the soil retention structure for the deep excavation.

Further projects utilising Airey Taylor’s expertise with longevity extension for corrosive forces include the $38 million Mandurah Aquatic Recreation Centre, and $31 million Claremont Football Club Development – both of which required careful engineering and materials selection due to exposed steel sections being subject to coastal corrosion – and the Majestic Walk Boardwalk using Airey Taylor’s groundbreaking work in the field of Glass Fibre Reinforced Polymers as reinforcement in concrete to create an enduring work rated for 75 years despite its corrosive and aqueous environment.