Upper Harbour Corridor Project
Bridge Duplication is Simply a Balancing Act
GOLDEN BAY CEMENT is playing a significant part in the construction of the State Highway 18 Upper Harbour (Greenhithe) Bridge Duplication and Causeway section of the Transit New Zealand Upper Harbour Corridor Project.
The Upper Harbour Corridor project consists of three parts. The
Greenhithe Deviation, the Upper Harbour Bridge Duplication and Causeway
Widening, and the Hobsonville Deviation. The motorway will extend from
the Albany Highway in the east across a new duplicate Upper Harbour
Bridge to the North-Western Motorway (State Highway 16) in the west.
Transit awarded Fletcher Construction the contract to design and
construct the $36.7 million Upper Harbour Bridge Duplication and
Causeway section, which connects the western and eastern ends of the
Greenhithe and Hobsonville sections of the Corridor by duplicating the
existing bridge across the Upper Waitemata Harbour.
The new bridge
will provide three eastbound lanes, plus a combined cycle and
pedestrian lane, while the existing bridge will service two lanes of
west bound traffic. Also included in the contract is the construction
of both the western and eastern approaches to the existing and new
bridges. This includes widening of the 850 metre long western causeway
and a 100 metre long section of road works at the eastern end.
The three lane bridge being built by Fletcher Construction is a 458
metre long cast in situ post-tensioned single cell box girder bridge
which is being constructed by the balanced cantilever method, over
seven spans, and a 67 metre land based approach section of hollow core
precast beams over three spans.
On the day we visited the site with project Quality Manager Dennis
Matulovic for the purpose of this article in late May, the Fletcher
Construction team were working on the installation of the cofferdam for
pier four and were preparing to cast segments on piers two and three.
Work was also continuing on the Causeway.
There are a total of 26 piles ranging in size from 1200mm to 2400mm and six piers and two abutments.
The general appearance (profile) of the new bridge will be similar to
the existing bridge even though it is some 8 metres wider.
The
850 metre long western causeway has been designed to make use of
available materials. 1,400 tonnes of Golden Bay Cement was added to
14,000 cubic metres of marine mud to produce 'mudcrete'. Mudcrete, sand
and granular materials were used below the water level, whilst cohesive
soils were placed on the causeway above water level.
The bridge structure will contain 8,350 cubic metres of concrete with
the majority being 45MPa concrete. In the high exposure category zones
concrete characteristics are being enhanced by the addition of
Microsilica 600. 90 tonnes of Golden Bay Cement will also be used in
the grouting of the post tensioning ducts. The Upper Harbour Bridge
Duplication and Causeway section of the project is due for completion
in mid-2006.