Extension of the metro line 11: the sliding of the tunnel in Rosny, a key step in the work
Indeed, if the construction of a viaduct and an elevated station is necessary to overcome the difference in height of the land between the La Dhuys and Rosny-Bois-Perrier stations, the metro will then become underground again by plunging under the motorway to reach the future terminus of the Rosny-Bois-Perrier line. This requires the installation of a tunnel under the motorway in record time to limit the closure of the A86 as much as possible.
Shifting in detail
The sliding consists of sliding the future tunnel into its final place, i.e. under the A86 > A3 slip roads. Here are the different stages of this exceptional technical challenge:
- The demolition of the A86 carriageway
The structure of the motorway ramp will first be dismantled, then an embankment will be dug in a second phase to make way for the reinforced concrete frame structure. - The sliding operation
The frame of the future tunnel is gradually being pushed from its platform to its final position. This operation lasts between 20 and 24 hours depending on the weather conditions.
- The reconstruction of the motorway
Once the shifting is complete, the road is reconstituted, the road elements are put back in place, as well as the road markings and guardrails, in order to allow a resumption of road traffic as quickly as possible.
This exceptional operation has been prepared since 2016 and developed in close consultation with the State, the managers of non-conceded motorways in Île-de-France and local authorities to limit the impact on users. It requires the closure of the A86 > A3 slip road towards Bondy from the evening of 8 August to the morning of 14 August.
Progress of the work
This exceptional operation was carried out in just over 5 consecutive days, from 8 to 14 August. This short time slot, identified as one of the slowest periods of the year and therefore the least impactful for users, represented a real race against the clock, during which the teams of the RATP and NGE, a public works company, took turns 7 days a week, 24 hours a day.
The demolition of the motorway, the shifting of the tunnel and the reconstruction were completed with the reopening of the A86 on Tuesday 14 August at 3 am, one hour ahead of schedule.
On this occasion, a vast communication plan had been deployed upstream on the road network and the digital tools of Île-de-France Mobilités and RATP in order to warn users of this closure and to inform them of the alternative routes available to them.
The Project at a glance
To support the urban development of the eastern Ile-de-France region, the extension of line 11 plans to serve several municipalities characterised by major changes: Les Lilas, Montreuil, Romainville, Noisy-le-Sec and Rosny-sous-Bois. 6 new stations will be created: Serge Gainsbourg, Place Carnot (whose name is provisional), Montreuil-Hôpital, La Dhuys, Coteaux Beauclair and Rosny-Bois-Perrier. This extension includes 6 km of new tracks, covered in 12 minutes when it is commissioned. The entire line will be covered in 24 minutes from Rosny-Bois-Perrier to Châtelet compared to 55 currently. Nearly 10,100 passengers will use this new extension during morning rush hour.
Map of the extension of line 11
New rolling stock will be deployed on line 11, with the order by Île-de-France Mobilités for 20 new trains. The latter will benefit from better comfort and better isolation from external noise, in addition to having the advantage of energy consumption reduced by 20% compared to previous equipment (LED lighting, electric braking, etc.). The warm and refrigerated ventilation will allow you to feel a feeling of well-being on board whatever the season
Work began in 2016, with commissioning scheduled for 2022.
RATP and Île-de-France Mobilités are jointly managing the project. RATP is overseeing the completion of the extension of the line as well as the process of modernising the stations, and Île-de-France Mobilités is ensuring that the project runs smoothly and that costs and schedules are respected.
The project to extend line 11 is financed by the State, the Île-de-France Region and the Société du Grand Paris to the tune of 20%, 46% and 28% respectively. The adaptation and modernization phase of the stations is covered by the State at 11%, the Île-de-France Region at 26%, the city of Paris at 29% and finally the RATP at 34%. The operation and rolling stock of the line are 100% financed by Île-de-France Mobilités.
To follow the progress of the work and for more information, you can consult the website dedicated to the project: www.prolongementligne11est.fr/