Major surgery for art gallery
Christchurch Art Gallery is getting "keyhole surgery" to raise the 30,000-tonne building millimetre by millimetre.
After the earthquakes, liquefaction under the building caused it to settle up to 150mm lower on one side. To re-level it, and raise it slightly, about 100 cement columns have been drilled 10 metres into the ground through the bottom of the underground car park to provide a platform.
The columns are created by drilling a small hole through the foundation and sticking a pipe down that releases high-pressure grout - a stronger and faster-setting form of concrete. This mixes with the natural soils around it to create a 4m-wide column.
The columns stop about a metre below the foundation.
Aurecon technical director Stephen Hogg said several shorter pipes were inserted through the foundation into these voids with quick-setting grout pumped in small bursts against the columns.
"These harden in seconds, pushing down against the columns. The next burst of grout shoots against previously hardened grout, pushing off it and slowly raising the gallery upward a millimetre at a time."
Hogg said it was the equivalent to performing "keyhole surgery" on a building as everything was controlled above ground with a computerised system operating the grout injections through small holes on the ground. It is the first major building in New Zealand to have the technology used on it.
The re-levelling is due to be completed by the middle of next month.
After this, work will continue on other parts of the gallery, including fixing cracks and the glass facade.
Fixing the gallery will cost about $56 million, with the re-levelling and lifting costing about $17m.
Christchurch Art Gallery Te Puna O Waiwhetu director Jenny Harper said the gallery's 6500 pieces were safely secured within the building.
However, it needed to be have a "gold-plated engineering certificate" so international and local galleries would feel confident lending exhibitions to it.
When the building reopens in the second half of 2015, Christchurch will have been without an art gallery for more than four years.
- The Press
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