Sangatte shaft

Diameter : 55 meters
Depth : 65 meters
In 1987, construction of the Channel Tunnel began in France at Sangatte on the Nord-Pas de Calais coastline at a location just over 3 kilometres away from the French terminal site at Coquelles..

A circular access shaft, 70 metres deep and 55 metres in diameter was excavated and lined with concrete. A hangar -like shed was built to shelter the shaft in the centre of the large construction site which also contained offices and a lining segment manufacturing factory

All materials, workers and equipment were lowered down the shaft to the working platform at 47 metres, where the tunnel boring machines (TBM) could be assembled in dry conditions.

From this point, three machines excavated the undersea rail tunnels and service tunnel beneath the seabed towards Kent and two boring machines began the drive underground and inland towards the terminal site. One of these machines was then re-assembled to excavate the second running tunnel, thus using only 5 machines on the French side.

Gantry cranes with pulleys were used to lower the TBM sections and subsequently the concrete lining segments.

Once tunnelling began, construction trains with a variety of wagons were used to transport the linings, the spoil and the workers. A railway control room at the top of the shaft regulated the movements of all the construction trains.

At the base of the shaft, a spoil treatment plant mixed the waste rock with water before pumping it 500 metre to the disposal site at Fond Pignon.

Once construction work was complete , the Sangatte shaft was transformed into a permanent feature of the tunnel system, housing the ventilation and cooling system installations.

The rest of the construction site has been landscaped and rehabilitation work continues with environmental monitoring of the Fond Pignon site.