The circular shaft has reached 26 m depth

The SWS Engineering Team is in charge of the detailed design of temporary and final structures and of the BIM modelling of the shaft and the cross passage. We congratulate the “équipes” of the construction companies joint venture NGE-Salini Impregilo for this first goal achieved.

On the Grand Paris Line 14 project, the excavations of the circular shaft Union/RN7 has achieved the depth of 26 m!
It is the deepest open pit excavation on the Lot 4 and it will serve as emergency exit and water exhaust for the main tunnel.

Due to aeronautical constraints, the diaphragm wall technique was not feasible and a tradition excavation, with step-by-step primary lining installation, has been performed.

The shaft cross different geologies and has three mains support sections :
– In the upper part, an injected ring is provided to isolate the excavation from the travertine’s water table.
– At the centre, a reinforced supporting section is designed to face the earth pressure of the over consolidated and swelling clays.
– At the bottom of the excavation, the shotcrete is reinforced with steel rebars and no other propping structure is necessary for the cross passage opening.

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