When a tunnel boring machine breaks through, a lot of rock and earth falls down. At the same time, stones fall from the hearts of those involved.
For us at VMT, the main challenge was the big TBM in a relatively small starting shaft. We are proud of the great work by the surveyors measuring the starting position of the TBM and of all VMT equipment having worked reliably during the project:
- Guidance system with TUnIS.moving station
- RCMS (Ring Convergence Measurement System)
- Segment production management with SDS onsite and LIS services during production
Further, the contractor used a special ring design with left and right tapering. It was not allowed to put the key stone between 90° – 270°. To meet this requirement, the team mastered the starting situation with the flying launch to bring the ‘big girl’ on track.
The ‘big girl’ we are talking about is Jill.
Just like its namesake, Jill Viner, the huge TBM is an innovator. While Jill Viner became the first female bus driver in London in 1974, EPB Shield Jill is the biggest TBM to be turned so far.
Why was it necessary to turn a machine weighing 2,300 tons by 180°?
“The U-turn manoeuvres were part of Riverlinx CJV’s original tender,” explained CJV Riverlinx project manager Ivor Thomas in an interview with the Tunnelling Journal The aim was to get the job done as quickly as possible, as there will be no return on investment until vehicles start to drive through the tunnel.
If you have ever tried to drive through the Blackwall tunnel at rush hour, you will understand why a second tunnel is needed.
Besides the reduction of delays and queues in the old Blackwall Tunnel, the new connection reduces the environmental impact of traffic congestion on some of London’s most polluted roads.