PREFABRICATION OF SEGMENTS AND RAILWAY CONCRETE SLEEPER BLOCKS

 

PREFABRICATION OF SEGMENTS

DIMENSIONNING

The factory and storage of the segments was industrialized and designed so as to ensure continuous delivery to the 5 tunnel boring machines.

CONCRETE LINING OF THE TUNNELS:

The concrete rings of the running tunnels are constituted of 6 segments including a trapezoidal key with a length of 1.60 metres.

The rings of the service tunnel are 1.40 metres in length.

Seals located on the lateral faces of the segments ensure water proofing.

The factory consists of:

• A steel reinforcement cage workshop of 12 800 m2 and a concrete casting workshop of 10 800 m2,
• A concrete batching plant producing 2 times 60 m3 per hour and produced up to 1 200 m3 in 24 hours.
• A storage space of 24 800 m2 equipped with 5 bridge cranes to receive up to 1 600 rings of the running tunnels and 1 100 rings of the service tunnel.
• A workshop and service buildings of 4 000 m2.

 

PREFABRICATION:

The cages are built using automatic three dimensional welding. (35 690 metric tons of steel were used and up to 460 cages produced per day)

The concreting of the segments are made in a carousel of 44 segment moulds with high vibration frequency.

After smoothing of the upper surface, the moulds are dried off for 7 hours and then checked.

The segments are then stored under bridge cranes in 5 different spans corresponding to the different type of segments.

 

DELIVERY TO THE TUNNEL BORING MACHINES

The segments, assembled per ring, are set up on pallets, are then conveyed to the shaft on mobile gantry cranes then carried by wagons to the TBM.

FINAL ASSESSMENT

The prefabrication factory employed 520 workers (2 350 000 hours of work).

The factory produced 252 310 segments necessary to 64, 3 kilometers of lining of the French tunnels. The quantity of materials used are 35 600 metric tons of reinforced steel, 550 000 cubic meters of concrete and 2 700 kilometers of seals.

 

INNOVATIONS

The performance of the high strength concrete used for the segments allowed a significant reduction in their thickness and weight, making their handling and erection easier with economies in the volume of materials.

The principle of self-controlling manufacturing quality control allowed for the reduction of losses and rejections to less than 2%.

 

MANUFACTORING OF RAILWAY CONCRETE BLOCKS

At the end of production of the segments; the factory was modified and the staff trained to accommodate the production of 340 000 concrete blocks for the Sonneville type railway tracks in the tunnels from Coquelles to Folkestone.