Lyttelton tunnel marks 50 years
Engineers working on the Lyttelton tunnel 50 years ago did not give much consideration to the region's potential earthquake risk, the man who spearheaded the project says.
The 50th anniversary of the opening of the Lyttelton tunnel was quietly marked this week, with an official celebration planned for May or June when the new tunnel control building was due to be completed.
The 1.9 kilometre Lyttelton road tunnel - officially opened on February 27, 1964 - was a joint venture between Fletcher Construction and American firm Henry J Kaiser Co and cost [PndStlg]3 million (about $120m today).
About 250 kilograms of explosives were used over three years to remove 150,000 cubic metres of rock from under the Port Hills, and the tunnel was lined with 1.5 million tiles.
Jack Smith, Fletcher's project manager for the tunnel construction, said the company had used geotechnical information gathered during the construction of the nearby rail tunnel almost 50 years earlier, but "surprisingly" not much attention was given to potential seismic risks.
"We did cross some faultlines and crush zones and signs of volcanic movement and things, but this was pretty normal in tunnelling work and no-one expected the earthquake in Christchurch."
The now 85-year-old said workers used pre-stressed concrete for the tunnel's ceiling which possibly explained why it stood up so well against the September 2010 and February 2011 earthquakes. "That technology was more or less in its infancy at that time," Smith said.
"I think we can take pride in that it was well-designed by the Ministry [of Works] and we engineered it well."
Smith planned to travel to Christchurch for the opening of the new tunnel control building later this year. The original building was damaged in the February 2011 earthquake and demolished last year. The category 1 heritage building was designed by late Christchurch architect Peter Beaven, who envisioned it as the "fifth ship" - after the four ships that brought the first European settlers to Canterbury.