"Installation by accurate ‘pipe jacking’ from the new inlet location, downhill, at approx 6.5% grade, 37 units (2.32m each), approx 86m of 1500mm internal diameter concrete Class 4 Humes “J” Series jacking pipe (supplied by the RTA) transversely under the F3 at Somersby, NSW at depth ranging from 7m to 14m below the Freeway."
To accomplish this challenge a Tunnel Boring Machine would be needed. Leed Engineering had put aside a certain amount of the project money to build a TBM. The TBM would be called ELNA 1800.
Ground conditions were favourable , sandy clay , the customer was the RTA in NSW , and we had 90 days to build a TBM and complete the bore. This included pushing 86m of concrete pipe behind a TBM.
The photo below shows the location of the bore in Somerby , NSW.
After some earnest discussion with senior management at Leed Engineering it was decided to kick-start the planning stage with all haste. A basic design was sketched up for a 1.8m external diameter TBM. Parts were sought and priced. Included in these was a new type of rock and stone cutter. This type of cutter is also known as Twin Headers or RoadHeaders or Rock Grinders. This Rock Cutter is the first of it's kind in Australia, and this piece of equipment goes well beyond the conventional,great speed and very maintenance friendly.
Below is the RoadHeader we had priced and specked up for the job.
Next was the design for the TBM itself. A large steel rolling company was located and were prepared to roll the 1.8m outer shells for the TBM. Planning was well on it's way with hydraulics ans electronic control systems all taking shape realy fast. A large Brivinni pipe jacking station was to be used to push allomg the 86m of concrete pipe. Although not new to TBM design, this would be our first go at using vacuum extraction technology. A gigantic vacuum plant with interceptors would be used to carry away the waste and dispose of it to EPA standards.
In reality we would be building a TBM that was a combination of the Herrenknecht pipe jacking TBM ,a Herrenknecht shaft sinking machine which works with a sweeping action and the giant TBM machine in India. See the pictures below , and CLICK HERE to see the animation of a pipe jacking TBM.
Engineering drawings were drawnup and the computer generated workings of the TBM were simulated to make sure all worked in harmony. Below is a structural drawing of Elna.
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The TBM would be assisted during the boring stage with a expanding and retractable jacking station inserted right behind the TBM head. The clip below illustrates the principal.
During a brainstorming session one evening we realized that it was going to be very risky to commit to the deadline requested by the client. Senior management at Leed Engineering made the right decision and informed the client the next day that we would not be able to meet there timeline. Although immensely disappointed, we all accepted and respected the solid decision.
What did we learn?
1) Respect for the client's timeline and his project is very important for future relations and projects.
2) If you can imagine it , you can build it!
3) Teamwork makes the world go round, or in this cases helps make the right decision.
I thank Leed Engineering for the opportunity to work and learn from them and hope that someday we will tunnel together.
Robbie Ashton from tunnel Bore Australia accepted the project and completed it in record time.