Title: Canning Dam Remedial Works, World.s Largest Permanent Ground Anchors

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Publication: CIA

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Date: 2/13/2011

Abstract:
Canning Dam is one of Perth’s major water supplies, and was well below currently acceptable safety standards. Structural Systems Limited has just completed upgrading the safety of the dam, installing almost 13km of the worlds largest capacity and longest permanent rock anchors. The advantages of an anchored solution include that it doesn’t outwardly change the dam’s appearance, and is often an economical and technically acceptable solution. Heritage issues often play an important consideration in engineering solutions; the use of permanent anchors is sensitive to this constraint. Prior to around 1980, the level of corrosion protection applied to .permanent. anchors was rudimentary by today’s standards. Testing has shown that at the interface of load transfer, significant grout cracking occurs and without a suitable impermeable barrier the highly stressed strands are vulnerable to accelerated corrosion through contact with water, oxygen and dissolved chemicals. Chloride ions are especially aggressive to the highly stressed strands and the working life of an anchor can be seriously jeopardised without appropriate defences. The importance of the bond length sheathing is now very clear, and the earlier anchors installed without suitable protection, should now be considered as temporary, and having an uncertain life expectancy.