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"The approximately 80 piles for the hospital’s outpatient building are being installed using a ‘bottom-driven’ technique," construction director Andrew Holmes said.
"Typically we commence with a closed-ended 12m steel tube and these are driven into the ground with a 14-tonne internal drop hammer [named "Hammeroid" by Otago Daily Times readers]."
As each tube was driven deeper into the ground, and depending upon the initial length of tube selected, it often needed to be extended before being driven in the final few metres in to the ground.
"Once the pile has been driven to the desired resistance and depth, between 14m to 22m, the steel tube is first trimmed back for excess and then filled with concrete, being completed with a high-capacity connection rod," Mr Holmes said.
Diggers and cranes have also been seen on the former Cadbury factory site in recent days.
Mr Holmes said work was not due to start on the site of the larger inpatient building just yet, and the machines were being stored there while not in use.