The tunnel boring machine (TBM), dubbed “÷Alice’, is the largest TBM ever to be utilised in the Southern Hemisphere and will help build New Zealand’s Waterview Connection, part of the Auckland motorway Western link.
With a length of 87 m and a cutting diameter of 14.46 m, the Herrenknecht EPB TBM No. S-764 is the tenth largest diameter TBM ever produced worldwide and weighs in at 3,102 tonnes.
Following efforts by the Well Connected Alliance (WCA) Tunnel Team, the TBM was built and sufficiently commissioned to meet the ready to bore milestone date of 31 October 2013, a date set two years earlier. This milestone was met by the WCA team through a spirit of collaboration between the civil works team, the site tunnelling plant team, and the major plant suppliers Herrenknencht, H+E and Grayson.
The Waterview team chose to implement an innovative method for the start-up of the TBM. Rather than using ten conventional reinforced concrete (RC) segments to make up a temporary ring, the team chose a combination of RC and steel segments to make up the temporary rings. This system greatly reduced the overall weight of the combined ring and removed any necessity for additional temporary support measures for the upper two-thirds of the temporary rings, thereby eliminating the need for the usual large A-frame steel support structures, steel wire rope cables, internal and/or external arch systems.
The team plans on bringing Alice up to speed over the coming weeks as they approach the location of the first Cross Passage (XP), where another special combination of RC segments and steel segments will be used to create the frame, through which the XP will later be opened.