THE Melbourne Metro Rail Authority says it be will up to the successful bidder* to decide whether giant tunnel boring machines used to build the Melbourne Metro tunnel are abandoned underground once drilling work is complete.
The monster machines, which are as long as a soccer pitch after being assembled underground, could literally dig their own graves.
Two of the 11 tunnel boring machines used to dig the Channel Tunnel between England and France were driven steeply downwards and abandoned once the 50km tunnel was created.
Melbourne Metro Rail Authority spokesman Reid Sexton said it was expected that the machines would be taken apart underground and their reusable parts brought back up.
But Mr Sexton could not rule out that some of the giant earthmovers would be parked permanently underground if that proved to be cheaper.
Abandoning the machines, which cost about $20 million, may cost less than bringing them out of the ground.
This is a decision for the successful bidder, Mr Sexton said.
“Up to six tunnel boring machines will be used during construction, each up to 100m long and weighing more than 1000 tonnes,” Mr Sexton said.
“These giant machines are a critical* part of the Metro Tunnel project, which will create more services more often to and from the suburbs”.
The $10.9 billion Melbourne Metro contract includes the excavation and fitout of twin 9km tunnels and five new stations at Arden, Parkville, CBD North, CBD South and Domain.
Up to six tunnel boring machines — nicknamed “moles” — will construct the tunnels outside the CBD and under the Yarra River with smaller machines used under Swanston St.
The mighty machines will be launched near the future Domain station and in the Arden St precinct.
As part of the tunnel entry the South African Soldiers memorial will need to be temporarily relocated.
The moles move about 10m a day and can operate 24 hours a day.
A rotating cutter head churns* through the ground with a conveyor belt or pipe carrying the excavated rock and soil to the back of the mole.
Vehicles and conveyor belts transport the extracted* material — enough to fill 800 Olympic-sized swimming pools — from the tunnel.
bidder: person or company who applies to do the job
churns: digs up
extracted: taken out
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Activity 1: Information Report
Write an information report to tell your audience about tunnel boring machines. Your report should include the following parts — a title, a classification (introduction), a description (three paragraphs explaining different aspects of the machine) and a conclusion. Ideas for your description paragraphs are explaining the size of the machines, how they work, where they are used, what happens to them when they have finished their job, etc.
Extension: Draw a diagram that shows how a tunnel boring machine works.
Extra resources: Examples of other information reports and/or an information report template may be helpful.
Time: allow about 40 minutes to complete this task
Curriculum links: English
Activity 2: (Not-so-) boring maths problems
1. If a tunnel boring machine can dig 10m per day:
a) how far would it dig in one week?
b) how far would it dig in April?
c) how far would it dig in one year?
d) how long would it take to dig 9km?
2. If an Olympic sized swimming pool is 50m long, 25m wide and 2m deep, what is its volume?
3. Take a piece of grid paper. Each 1cm line represents 1km. Imagine you have been asked to design a 10km train track loop. How many different designs can you come up with?
Extension: Try question 3 above again, but this time your track must be 20km.
Extra Resources : Calculators, grid paper
Time: allow about 20 minutes to complete this task
Curriculum links: Mathematics
(Vocabulary, Connectives, Openers, Punctuation)
Use the following Openers to write a quick sentence about the trains that will one day travel through these new tunnels.
– Before the
– We always
– Having decided
– An important thing
– As time went by
– Before very long
– Another time
– In addition
Time: allow about 10 minutes to complete this task
Curriculum links: English, Big Write, VCOP
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