2016 – Maintenance and Testing of Post-Tensioned Anchors for Dams and Appurtenant Structures

Sean Ladiges, Robert Wark, Richard Rodd

The use of permanent, load-monitorable post-tensioned, anchors for dam projects has been in place for approximately 35 years in Australia. Since then, over 30 large Australian dams have been strengthened using this technology, including the world record for anchor length (142 m – Canning Dam, WA) and size (91×15.7 mm strands – Wellington Dam, WA and Catugunya Dam, TAS).

In order to achieve the design life of 100 years expected of these anchors, an ongoing program of monitoring, testing and maintenance is required, to identify and rectify the initiation of corrosion or loss of pre-stress. Guidance for maintenance and testing regime for post-tensioned anchors in dams is provided in the ANCOLD Guidelines on Dam Safety Management (2003). The various conditions which may affect the performance of the anchor with time, such as anchor type, ground condition and loading fluctuations are not covered in the Guideline.

This paper reviews the implementation and results of anchor monitoring programs by Australian dam owners. The first part of this paper provides a summary of the testing and monitoring programs currently being implemented. The second part of the paper reviews the aggregated anchor load test results from a number of Australian dam owners, and identifies trends in anchor response over time following installation.

The paper aims to assess whether the recommended anchor testing regime proposed in ANCOLD (2003) is appropriate and cost effective, using evidence from recent load test data which has become available following the writing of the guideline. The lessons learnt from anchor maintenance programs will also be discussed.

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