2002 – Catagunya Dam – Corrosion Assessment of Fully Grouted Post-Tensioned Anchors

R.I. Herweynen and A.M. Hughes

Hydro Tasmania has a number of dams which were designed and constructed in the 1950-70s
with fully grouted, post-tensioned anchors. The method used was leading edge in its day,
however, it does not achieve the cable protection of modern methods which provide two barriers
against corrosion and are monitorable. Hydro Tasmania has developed and employed an
innovative program to ascertain the integrity and remaining life of the cables and to prepare
long term management plans for its cabled dams.

An international panel was set-up to provide guidance on the overall issue, assist in developing
a sound methodology for assessing the corrosion of the anchors and advise on long-term
monitoring. To focus the efforts, Catagunya Dam was adopted as the pilot dam, as the stability
of this dam is very much dependent on the integrity of the anchors. This paper will provide a
brief overview of the project to date but will focus in detail on the main components of the
corrosion assessment of the anchors, namely:

  • In situ ground water testing over the entire valley section using holes drilled for piezometers.
  • Laboratory testing carried out by CAPCIS in the UK to simulate potential corrosion rates
    using actual ground water samples collected.
  • In situ potentiostatic polarisation testing used to determine instantaneous corrosion rates forthe test anchors.

The paper also provides a brief summary of the instrumentation installed at Catagunya Dam to
assist with the long-term monitoring of the dam.

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