Moving the Virginie tunnel boring machine
The 1,500-tonne, 120-metre-long tunnel boring machine was successfully moved the 650 metres separating it from its reassembly platform at the start of digging.
Why this manoeuvre?
The site is located at the end of and in line with the take-off runways, which precludes most of the lifting operations required to reassemble such a machine. It was therefore more appropriate to relocate the reconditioning area and then move the complete machine once all the functional tests had been carried out. In addition, this ‘one-shot’ transport solution optimised the schedule for getting the TBM into its start-up configuration.
The Razel-Bec teams managed a large-scale operation using exceptional transport resources:
- Firstly, the operation required the shield to be raised, using high-capacity jacks (the front part, consisting in particular of the cutting wheel and the engine, weighs around 1000t). The shield was then raised by more than 2.50m, allowing 2 ‘centipede’ lorries (SPMT Kamag lorries with a capacity of 1400t from SARENS) to be slid inside.
- Secondly, our design office, D2i, together with our equipment department, designed a special trailer coupling to tow the 4 TBM trailers, which total around 500 tonnes. For safety reasons, the TBM's thrust jacks were coupled to this system to check the forces transmitted to this custom-made metal part, which is welded to the structure, throughout the manoeuvre.
- Finally, the road was not flat, with a 6% gradient for access to the finishing structure. A 3rd SPMT was therefore mobilised at the rear of the convoy, equipped with a giant winch to unwind a safety and restraint cable over the last 200 metres of steep gradient.
The transport operation lasted 5 hours, and all our technical hypotheses were confirmed.
Our equipment department should be commended for having developed an innovative and ambitious solution for transporting a complete tunnel boring machine, a first for the Grand Paris Express. We should also mention the ingenious system of ‘rollers’ installed under the trailers.
Special thanks also to the civil engineering teams who worked for 10 months, a very short time, to achieve this 1st objective of the Razel-Bec 17.3 worksite.
In the next few days, we will be finalising this TBM and its conveyor so that we can start digging the 6.2 km from the north to the south of Paris-CDG airport at the beginning of December.
