Metro Tunnel Case Study 2025
Melbourne’s Metro Tunnel is set to open in December, with five new train stations. But where did it all start?
Back in early 2019, the Metro Tunnel Project was about to start drilling its first major tunnel, when it realised it needed something for the huge Herrenknecht boring machines to push back against. A thrust frame, or push frame, as shown below, was built for this purpose.
The only other option was to have 1200 people stand behind the boring machine – which probably wasn’t going to work…
When a Herrenknecht 350 ton boring machine starts drilling horizontally into earth, there are massive forces at play. So the thrust frame needs to be secured to the ground, which involved huge custom-made reinforced WR-grade DSI steal thread bars, with unique threads.
Q: How do you secure these bars tightly enough, given they have a custom-made thread?
To secure these bolts, which hold down the thrust frame, the bars need to be pulled up into extreme tension, as the nut is further tightened.
Brett Blakemore (Flotek, Managing Director) said, “The bar tensioning is crucial in the early stages, as it holds down the main thrust frame used to push the Herrenknecht tunnel boring machine’s cylinders, to get the process started."
"Before the first part of the hole is created, there’s nothing to push against."
"Therefore, the bars holding down the thrust plate need to withstand an incredibly large force”.
Enerpac provided the equipment to do this tensioning, however, it’s not so easy when the steal thread bar has a custom-made thread. There needed to be something specifically designed, as there is no off-the-shelf product for tensioning custom made DSI thread bar.
This is where Flotek stepped in. Enerpac approached Flotek to create a solution.
“There’s no off-the-shelf solution for tensioning DSI threadbar, so we had to create one."
"Given the thread bar was unique, and there were massive forces at play, coming up with a solution to tension these bars took us around 2 weeks."
"It incorporated an Enerpac RCH603 hollow cylinder tensioner with spring return, with an Enerpac P392 pump.” Brett Blakemore
Brett explained, “The Enerpac RCH603 hollow plunger cylinder is ideally suited for this tensioning task, as it can safely and efficiently provide up to 567KN which is equivalent to around 65 tons of force, which is actually more than we needed for the Metro Rail tunnel.”
Before this solution could be used, it needed to be tested on site.
“The feedback from the Metro Tunnel Project site engineers has been very positive. The system is working exactly as intended, with no issues.”
This unique bolt tensioning tool created by Flotek, which is all about tensioning anchor points, or stud tensioning, has also been used on other Melbourne infrastructure projects such as the Westgate Bridge.
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Flotek has been Australia’s leading hydraulic service company for more than forty years. With a fleet of highly trained hydraulic technicians, and a state-of-the-art cylinder repair facility, we’ve supplied hydraulic expertise to most of Melbourne’s major infrastructure projects including North-East Link, the Westgate Tunnel Project, and the Metro Tunnel project.
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