The Waterview Connection project is New Zealand’s largest infrastructure project, currently under construction and due for completion in early 2017. At the heart of the project lie twin EPBM tunnels, currently being constructed by the Mega-TBM, known as Alice.
We took the opportunity to interview Iain Simmons, Construction Director of the Well Connected Alliance, responsible for the delivering this important Mega-TBM project, ahead of the 13th Australian Tunnelling Conference.
Could you give us a brief overview of the project and the stage that the project is currently at?
The NZ Transport Agency’s $NZ1.4b project is the final connection of motorway to link SH20 to SH16, providing a second motorway link North – South through the city of Auckland, NZ. This motorway link will also improve connectivity between the South and West of the city, provide a direct link from the busy Auckland airport to the CBD, and better connect Auckland with its regional neighbours. The link is around 5km in length and features a twin tunnel section of three lane motorway 2.4km long with cross passages connecting the twin tubes at 150m centres. At the north of the project the connection to SH16 features four elevated ramp sections, ventilation building and remote ventilation stack connected by cut and cover tunnel. In the south of the project there are over bridges, footbridges and a ventilation building. The project features extensive urban design elements including footpath/cycleways, playgrounds, skateparks, sports fields, basketball courts and BMX track as well as an extensive programme of native planting.
The excavation of the first of the twin tunnel was completed last year with the second tunnel due to breakthrough in mid-October. Cross passage excavation started in June 2015 and is progressing well with the excavation due to be completed later this year. Mechanical and Electrical fit out of the tunnels has commenced along with the invert filling operations and deluge drainage system. Works at the northern connection to SH16 are well advanced with the third elevated ramp due to be completed later this year. In the South the pavement construction is completed up to the lower layers with much of the landscaping works well advanced. The project is on track to open in early 2017.
The project has drawn global attention, given its status as one the world’s mega-TBM projects – what are the unique conditions or features of working with a TBM of this scale?
Large TBM’s like Alice require some pretty intensive planning to enable them to work efficiently. Getting the TBM built was a huge undertaking with the logistics of getting her to site then the temporary works required to actually build her. The main drive unit and assembled cutterhead both weighed in excess of 300Te. The temporary works needed to launch the 2400Te shield section of Alice also had to be well designed and the potential thrust loads generated by the TBM are around 30,000Te.
Once the TBM is operational then the logistics become the main concern. On a good day Alice can produce over 8000Te of spoil with moisture contents between 30% and 40%. This spoil needs to be taken off site and dryed, then placed as a structural fill. For each ring excavated the TBM requires 20cum of grout to be placed in the annular void outside the ring. Segment production, storage and transport also present unique challenges with over 24,000 units required, each full segment weighing around 10Te.
Finally there were some pretty unique challenges moving and turning Alice at the northern portal to allow her to construct the second tunnel. At 2400Te and 14.45m in diameter the shield section of Alice was a considerable sized TBM to move. The planning and temporary works design for this innovative and successful operation was a huge undertaking for the project.
What innovative technologies or approaches have been used during the design and construction phases?
What advantages have they brought to the project?
Careful control of the TBM during launch allowed the use of lightweight steel thrust rings during the two launches of Alice. This meant that the ring support structures could be significantly smaller and lighter than would be otherwise required.
There is a culvert provided in the invert of the tunnel to house the services needed during the operational life of the tunnel. The culvert was installed using a separate self-propelled laying gantry. This innovation allowed the culvert laying to proceed without affecting the normal TBM activity and thus ensured that optimal production was achieved by both the TBM and the culvert laying operations.
Other innovations were used to allow the operation of the TBM in “short mode” during the construction of the first section of tunnel #2, which allowed for a reduced footprint in the northern portal structures, saving cost and time.
It was decided early on that the procurement for the project would adopt an Alliance model. What benefits has this approach brought to the project and the Alliance members?
The Alliance model has brought together three designers and three contractors who have the combined skills required to deliver the project and aligned them with the client NZ Transport Agency. This has ensured that the project is well resourced with suitably experienced people and by working together collaboratively alongside the client a very effective delivery model is created. One of the key elements of this Alliance is the creation of a strong culture of open and honest communication, with an emphasis on working safely and treating people fairly. The Alliance model has enabled us to achieve our goals so far on the project and will ensure that the opening of the project and then the operating phase will be efficiently tied back into the rest of the motorway network.
Did you have a unique or funny fact about the project that you can share with us?
The shield section of Alice weighs more than 400 fully grown African bush elephants.
Which projects are you looking forward to hearing about and what discussions are you looking forward to having with your peers at the 13th Australian Tunnelling Conference?
I am really interested in the two international projects featured in the conference, the Follo line project and the LA County MTA projects. In terms of discussions, its’ just good to have the opportunity to catch-up with people and find out what’s happening in the world of tunnelling outside of New Zealand.
Want to know more? Iain Simmons will join the speaker line up for the 13th Australian Tunnelling conference in October 2015 to present an update on the Waterview Tunnel construction, project progress and some of the of the major project milestones achieved to date.