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Ian Walsh

Ian Walsh

Ian Walsh is a civil engineer who studied initially at Canterbury and later pursued further studies in geotechnical and dam engineering at the UNSW in Sydney.  He is employed as technical services manager with Opus International Consultants based here in Dunedin, and he has a long involvement with water resource engineering covering irrigation, hydro-electric development, and municipal water supply. 

Ian has a specific interest in dam design and dam safety management, and it is in this context that he was active over a period of several years during the early 1990’s on the refurbishment of several aspects of the Waitaki dam.  In seeking to understand the mindset of the original designers and constructors of the dam, he has needed to grasp the changing state of technical knowledge that has occurred since the 1930’s, particularly in fields such as rock mechanics and seismology. 

Ian is currently design leader for several small hydro developments, and he provides technical assistance to regulators administering the new statutory dam safety regime under the Building Act.  He also leads the provision of risk management services for a range of clients covering infrastructure asset development, asset management, and service delivery activities.

Paper: Waitaki Dam - 75 years On

Abstract: The Waitaki Dam situated on the lower Waitaki River on the east coast of New Zealand’s South Island was constructed between 1928 and 1934, a period influenced by the effects of the great depression. The overspill concrete gravity structure is historically significant in several technical respects. This was the first hydro-electric generation scheme developed on a major South Island waterway, and aspects of the design and construction presented challenges that were new to New Zealand engineers. International design review during construction identified shortcomings in the understanding of uplift pressures on the stability of the dam blocks, resulting in an additional drainage gallery being retrofitted to the heel of the dam outside of the upstream face. Closure of the diversion sluices presented a major difficulty as three gates overshot their seat and were unable to be raised back into position under the pressure of the rising lake. An innovative sealing detail was developed, but the bitumen used at the time to grout the final opening has been subject to extrusion over the years. Adequate stability of the dam blocks under uplift and extreme loading including earthquake events has been an ongoing matter of investigation and analysis over the life of the dam as engineering knowledge has progressed. In 1961 a major anchoring project was completed, where the dam blocks were secured to the foundation by up to 300 ton capacity stressed and grouted cable anchors. Predicting the reliability of the long term performance of these fully grouted anchors has presented difficulties, and further uplift control improvements were completed in the early 1990’s to improve confidence in the performance of the dam.

Keynotes
Sir Neil Cossons
Paul Davies
David Dolan
Wayne Johnson
Euan McQueen
Robert McWilliam
Duncan Waterson
Authors
David Beauchamp
Trevor Butler
Matthew Churchward
Andrew Cleland
Rachael Egerton
John Fitzmaurice
Don Fraser
John Gibson
Owen Graham
David Hamilton
Bill Harvey
Peter Holmes
Kevin Jones
Paul Mahoney
Tom Williamson
Peter Lowe
Peter Marquis-Kyle
Gavin McLean
Rob Merrifield
Owen Peake
Miles Pierce
John Porter
Nigel Ridgway
Tony Silke
Jim Staton
Richard Venus
Ian Walsh
Daniel Woo
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