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Contractors World International Vol 6 No 1

New Zealand

TBM Alice starts second drive

One of the world’s largest tunnel boring machines recent-

ly started its second drive for the large-scale “Waterview

Connection” project in Auckland, New Zealand.

The first 2.4 km long tunnel was completed in September

after only eleven months. In the heart of the metropolis,

the Herrenknecht EPB Shield S-764 is creating the shell for

a road tunnel that will link two of the main State Highways

together.

The tunnel boring machine Alice has begun its second

drive in New Zealand. Earlier, Alice – named after the main

character of “Alice in Wonderland” – excavated the first

2.4 km long tunnel in just eleven months, with best perfor-

mances of 126 meters per week and 452 meters per month.

On September 29 at 1:45 p.m. local time the gigantic

boring shield finally broke through the wall to the first tar-

get shaft in Waterview.

The “Waterview Connection” tunnel project is one of

the largest infrastructure projects in New Zealand. The tun-

nel alignment runs below a densely populated residential

area and several parks.

The 2.4 km long link will become the longest road tunnel

in New Zealand. For this project, Herrenknecht designed a

machine concept perfectly adapted to the geological and

structural conditions.

With a boring diameter of 14.46 meters, the EPB Shield

S-764 is one of the world’s largest tunnel boring machines

of its kind. Its gigantic cutting wheel is driven by 24 electric

motors with a total output of 8,400 kilowatts.

It has relatively large openings for optimum removal of

the excavated material and has been specifically designed

for the expected geology.

In the first section the TBMwent through soils composed

mainly of sandstone and siltstone. The cutting wheels’ cen-

tral cutting tools could be changed from the rear area. The

ripper tools for softer grounds were thus replaced with disc

cutters for harder rock when needed.

In addition to the actual TBM with three back-ups,

which creates the tunnel shell, Herrenknecht designed and

delivered an autonomous, fourth back-up.

This followed TBM Alice at a distance on the first sec-

tion already. Its task is to lay a “tunnel within the tunnel”.

It creates a part of the tunnel invert that supply lines will

later pass through.

This method of operation fully independent of the TBM

advance offers an important advantage: advance perfor-

mances of the TBM and the lining of the invert do not limit

each other and can be done in parallel to save time.

After the first breakthrough the TBM and the first back-

up were turned by 180 degrees in a very tight space and

moved to the starting position for the second drive.

Because of the limited space, a temporary second back-

up, also supplied by Herrenknecht, was docked onto the

machine. In the initial phase it is responsible for the exten-

sion of the supply and disposal lines.

With it, Alice is now boring an approximately 300 meter

long “launch tunnel”. After this first part of the second tube

has been driven, the original configuration with the longer

back-ups 2 and 3 will be re-docked to the TBM. Then Alice

will get going at full speed.

The shell of the second tube is due to be completed in

2015. The opening to traffic is scheduled for the beginning

of 2017.

Herrenknecht