Largest transport project in Europe

By constructing 200 km of new metro lines, Paris launched the largest transport project in Europe. The Grand Paris Express will ensure accessibility in the future while making Paris ready for the 2024 Summer Olympics. The total project consists of 4 new metro lines (lines 15 till 18) and the extension of two existing lines (lines 11 and 14). The new network will contain 200 km of new metro lines and 68 new stations. Construction work began mid-June 2016 and is due to last until 2030. By then, 2 million passengers will be using these new lines daily.

Prefabrication of temporary strutting systems

To facilitate the excavation, ArcelorMittal Foundation Solutions prefabricated the temporary strutting systems. The total contract not only concerns the delivery of 3,500 tons of tubes, beams, and plate material for the struts and walings, but also the tailor-made and specialised prefabrication necessary for the tubes and beams.

The job site is in the heart of Paris and has limited storage, thus leading to logistical challenges. ArcelorMittal Foundation Solutions ensured just-in-time delivery of the struts and walings for quick and easy assembly on site. The fabrication tolerances were very strict to ensure precise assembly on the job site. In 9 months in total 10 strutting layers were manufactured, delivered to, and installed on the job site.

Using materials from stock

Due to the availability of materials, the initial design was redesigned into a solution with materials from stock. During the redesigning phase, ease of installation and standardisation of the dimensions were prioritised. The struts were therefore segmented and equipped with head and couple plates so that exchange and reuse became possible. Subsequently, all waling parts were prefabricated in one piece, including angled strut heads and provisions for mounting on the walls of the building pit.

Special structures

Apart from the standard struts and walings, several special structures were designed and produced. To provide better access for the cranes and for lowering the building materials, locations were designated to create larger open spaces between the struts. These openings were created by using ‘Four Way Pieces’ or 'Pattes d'oie' as they are called in French. In total, four 'Pattes d'oie' were designed and prefabricated to redistribute the strutting forces over a larger part of the wall. As the adjustment possibilities on the job site were limited, even more, stringent tolerances were agreed and every strut with ‘Pattes d’oie’ was trial assembled in advance on the production location to make sure everything fitted.

Due to the delay of the Tunnel Boring Machine (TBM), the phasing of one station was changed during construction and an extra strutting level was required. This intermediate strut level was designed, which was incorporated in the permanent concrete structure. As the strutting heads of this layer were cast in concrete, special heads were fabricated. The material for the struts was reused from other already dismantled layers.