Work on Brisbane City Council’s US$790M North-South Bypass Tunnel is entering a new phase with the arrival of the first mammoth TBM. The machine entered the Port of Brisbane on 22 September, three months ahead of schedule.

This is the first of two machines that will be launched from Bowen Hills towards Woolloongabba to excavate the 4.8km of twin tunnels underneath the city of Brisbane, creating Australia’s longest road tunnel.

Painted in the green and gold of Australia, this massive machine is capable of cutting through the hard Brisbane ‘Tuff’ rock at a rate of 20m+ a day. And with further good planning will enable the project to be completed well ahead of the scheduled date of October 2010.

The machine has a cutterhead diameter of 12.4m making it the largest TBM ever used in Australia. It is a double shield gripper machine with a telescope section in the middle. The two pieces, the cutterhead and the gripper, can move independently of each other allowing the machine to continue cutting while the lining takes place.

Adam Hudson, construction director of tunnel builders LBB JV (a joint venture between Australian companies Leighton Contractors and Baulderstone Hornibrook and German tunnelling experts Bilfinger Berger) stated the project is entering an exciting phase.

“The sheer size of these machines is overwhelming, but they have been painstakingly designed and manufactured by Herrenknecht of Germany to take on the challenge of the hard Brisbane rock which has a compressive strength of between 80 and 150MPa, and the difficulties associated with tunnelling under a major river” he said.

The TBM is currently being assembled within a large purpose built shed at the main northern worksite in Bowen Hills. The erection of the shed and preparations for the arrival of the TBM was a massive undertaking for the works preparation team. At 120m by 90m the shed is the size of two football fields. The shed contains impacts on the neighbouring community such as noise and dust and will enable 24-hour tunnelling operations.

The TBM will launch in early December from the northbound tunnel launch chamber and will start its journey south through Fortitude Valley, under the Brisbane River and across Kangaroo Point, ending in Woolloongabba where she will be lifted out a year later from a purpose built shaft. A second identical TBM will commence the southbound tunnel drive early in 2008.

A year on

The arrival of the TBM coincides with the one year anniversary of construction. Whilst the TBM tunnel team has concentrated on preparing for her arrival, surface crews have been creating the links between the tunnel and the existing road network.

The initial work included site mobilisation, identification and relocation of underground utilities and the development and approval of traffic management plans. A year later and the sites are now stabilised and ready for the cut-and-cover excavation of the tunnel entry and exit ramps. In addition, work is progressing well on creating a complex three-level road interchange in Bowen Hills which spans an arterial road, major railway yard and a creek. The bridge team is using a hi-tech bridge girder launching structure to negotiate these obstacles and to reduce the worksite footprint by eliminating the need for large mobile cranes to be set up on an extremely congested site.

The conventional tunnel team have been hard at work underground since February 2007. There are now seven roadheaders in operation and over 650m of tunnel has been excavated to date. The focus for this team has been the excavation of a middle section of the tunnel where the Kangaroo Point on ramp converges with the mainline and a 250m section at the northern end of the southbound tunnel. These are both sections where three lanes merge into two. The TBMs need to be pulled through these sections and so it is critical that they are ready in time for their arrival.

Project challenges

The tunnel team is systematically managing the challenges and complexities associated with tunnelling through Brisbane’s hard rock. Two major types of rock have been encountered, the Brisbane ‘Tuff’ – a welded volcanic ash and the Neranleigh-Fernvale metamorphic rock both of which are very strong and very stable. Extensive geological investigations have been completed and will continue throughout excavation and to date; the rock is behaving as predicted.

Another challenge for the tunnel and wider project team is water, firstly the availability of town water and secondly during excavation underneath the Brisbane River.

LBB identified early that South East Queensland was heading towards tough water restrictions and so put measures in place to recycle and treat all tunnel water through ultra filtration water treatment plants, augmenting that with a 600,000 l/day seawater reverse osmosis plant which draws water from a nearby creek. In an Australian first, these facilities have effectively ‘drought proofed’ the project by eliminating the use of town water supplies for construction purposes.

Tunnelling underneath a water table is always a challenge, although no particular water bearing features have been identified for the sub aqueous section of the tunnel drives. Notwithstanding this, LBB have the ability to deal with the issue of finding unexpected water when excavating under the Brisbane River. Adam Hudson explains “we will be probing at least two tunnel diameters and up to 30m ahead of the face, looking for any vertically formed features that are water bearing. If water is present then we will grout this prior to continuing the excavation. We are also able to seal our telescope section, the gripper penetrations and the muck ring should we get an unexpected inundation”. In addition, water can be controlled both during and after construction as the tunnel will be a fully tanked/lined tunnel.

Lining up

The tunnel will be encased in a 400mm thick concrete lining. Each TBM has the capability of installing 90 segments per day and over 37,000 segments are required to fully line the tunnel. To meet the demand LBB have built a precast segment manufacture facility and concrete batching plant in Pinkenba close to Brisbane Airport.

Adam Hudson states the facility uses the latest concrete and robotic welding technology, “the precast facility will be utilising three automated welding systems for the fabrication of the reinforcement cages for the precast segments.

“The segments are stockpiled at the facility to enable the 180 segment/day demand to be met. The facility is capable of producing up to 100 segments a day and can store up to 9,000 segments on site,” says Hudson.

The Precast Facility is staffed by up to 100 people, working two shifts, on a 24-hours a day basis.

Spoil removal

Almost 3.5M tonnes of spoil will be excavated during the three year construction period. Between 60-70% of this will be used as the structural sub-grade sub-base layer for development land at the Brisbane Trade Coast site (old Brisbane Airport). This is a major benefit for the region avoiding the need to use selected quarry overburden to meet the strength, compaction and durability specifications for such an application. 10% of the spoil will be used to stabilise the lower pavement layers of NSBT road work and the remainder will be reprocessed by the spoil disposal contractor. For example, some of the rock has been provided to local churches for restorative purposes.

A material handling facility is currently under construction in Bowen Hills to handle the TBM spoil. The spoil will be transported from the machine via an enclosed conveyor system back to the facility for processing and loading onto trucks. The whole operation will be enclosed to minimise the impact on the local community and to enable the 24-hour removal of spoil. The trucks will follow the arterial road network and will be fitted with GPS navigation to monitor the routes and to assist with vehicle arrival and departure times to and from site.

Project people

Up to 1500 people will work on the project at the peak of production. This includes 350 LBB staff, 200 consultants and 950 construction workers and subcontractors. The majority of staff are now on board and comprise of a mixture of local, interstate and international expertise.

The teams from major subcontractors Herrenknecht and United Group Infrastructure have mobilised and are eager to move from the planning to implementation stage. Herrenknecht are the manufacturer of the TBMs, spoil conveyor systems and segment facility and United Group will provide the M&E fit-out of the tunnels.

Most of the design work for the 200-strong Maunsell Parsons Brinckerhoff JV is complete and the team have now started to demobilise.

All systems go

A year on and the project is well and truly underway. Adam Hudson said that the team have been preparing for the arrival of the TBM for some time and are eager to complete the assembly.“It’s a very exciting time for us and we are looking forward to launching our first machine in December this year, and to do so three months ahead of schedule is a great result” says Hudson.

The second TBM set sail from Rotterdam on 4 October and is expected to arrive in Australia in mid November.

North-South Bypass Tunnel Overview

The North-South Bypass Tunnel (NSBT) is 6.8km long and includes dual twin lane tunnels, approximately 4.8km in length with connecting ramps to and from the Inner City Bypass (ICB) and Lutwyche Road in the north and the Pacific Motorway and Ipswich Road in the south. A connection to Shafston Avenue in Kangaroo Point will also provide access to the eastern suburbs.
It is the first project to get under way as part of Brisbane City Council’s Transport Plan for Brisbane (2002 – 2016) and the Lord Mayor’s TransApex Project – the biggest urban road project proposed in Australia aimed at filling gaps in Brisbane’s transport network to allow traffic to bypass the CBD.
Brisbane City Council chose to deliver the NSBT using a Public Private Partnership (PPP) model that will see the private sector consortium, RiverCity Motorway (RCM), build, own, operate and maintain the tunnel for approximately 45 years.
RiverCity Motorway has contracted the design and construction of the tunnel to the Leighton Contractors and Baulderstone Hornibrook Bilfinger Berger Joint Venture (LBB JV). This joint venture unites the infrastructure expertise of Leighton Contractors and Baulderstone Hornibrook and also the tunnelling experience of Bilfinger Berger.
LBB has enlisted the help of the following consultants:
– Maunsell Parsons Brinckerhoff JV: Principal engineering design
– Bilfinger Berger Technical Bureau: Permanent tunnel lining design
– Golder Associates: Geotechnical engineering
– EDAW: Urban design and landscape architecture
– United Group Infrastructure: Tunnel services and traffic management systems
Leighton Services and Bilfinger Berger Services will maintain the North-South Bypass Tunnel during the concession period.

Machinery Overview

Two double shield Tunnel Boring Machines:
Cost – US$44.4M each
Design and manufacturer – Herrenknecht, Germany
Weight – 4,000 tonnes
Diameter – 12.4m
Length – 261m
Tunnel support – concrete segment lining

Eight Roadheaders:
2 x S300 Mitsui
4 x T3.20Q Wirth with Inline heads
2 x AM105 Voest Alpine
Weight – up to 130 tonnes
Tunnel lining – bolts, shotcrete, lattice girders and canopy tubes

Assembly of the 12.4m diameter Herrenknecht TBM on site The Herrenknecht team members assemble in front of the machine Fig 1 – project alignment