Paris advancing its mega metro expansion 13 Jul 2017

In 2030 Paris expects 10.5 million passengers to use the city’s metro every day, initiating the need to expand the current system as used by 8.5 million travellers per day. To deal with the expected 2 million growth increase, the city has chosen to construct a 205km orbital network which will connect the city suburbs to each other.

Commercial development is planned at each of the new Grand Paris Express stations as illustrated for the new Villejuif Station on Line 15

At the moment Paris has a radial mass transit network. All metro lines head from the suburbs directly into the city centre. Commuters travelling from one suburb to another are forced to do so by taking a time consuming journey through the heart of the city. Driverless trains running at 85 second intervals will carry passengers between 68 new stations on the new orbital line, 51 of the stations connecting to the exisiting radial lines (Fig 1).

While the €25.9 billion (US$29 billion) orbital network will relieve the enormous pressure and congestion on the existing radial lines, the key driving factor behind the Grand Paris Express is urbanisation. “The suburbs surrounding Paris city centre are densely populated and growing rapidly, with more and more people needing to travel between the suburbs only,” explained Vincent Baumont, Deputy Director of the Mission of Project Management Consulting of engineering company Arcadis. “It would therefore make most sense to connect all these suburbs with each other by a ring line and thus avoid crossing Paris.”

Map showing the four new metro lines and extensions

Social and economic development is another driver of the project. The Société du Grand Paris (SGP) not only wants to build a new metro system, it also wants to maximise the benefits for the growing suburbs at the same time. “We will develop the property surrounding all new stations into lively neighbourhoods to support local economic growth,” said Baumont.

Four new lines

Construction of the Grand Paris Express started officially with a ground breaking ceremony for the Line 15 South in June 2016. As one of four new lines with Lines 16, 17 and 18, Line 15 will become the main part of the project, running 75km underground following a loop around the edge of downtown Paris and connecting all the closest suburbs.

The 26km-long Line 16 more or less extends Line 15 and gives access to the more remote suburbs in the north-east of Paris. Line 17 will become 28km long and will branch off Line 16 to connect with the Charles de Gaulle Airport to the north of Paris. The 35km-long Line 18 will connect Orly Airport and suburbs to the south-west of Paris with the city centre. In addition to the new lines, which are planned to open in stages between 2022 and 2030, the existing Metro Lines 11 and 14 are to be extended.

In February this year (2017), Société du Grand Paris awarded two of its largest construction contracts for the project so far, valued at €926 million and €807 million, both for two separate lots on the southern part of Line 15. The €807 million contract was awarded to a consortium lead by Bouygues Travaux Publics and with Soletanche Bachy France, Soletanche Bachy Tunnels, Bessac and Sade for excavation of a 6.6km x 8.7m diameter twin-track running tunnel, four underground stations, a 1.1km x 6.7m diameter tunnel and a launch shaft for two TBMs. This contract will run from the Villejuif Louis-Aragon to Créteil I’Échat Station (Fig 1). The €926 million contract was awarded to a consortium of Vinci Construction Grands Projets (leader), Spie Batignolles TPCI, Dodin Campenon Bernard, Vinci Construction France, Spie Foundations and Botte Foundations for five stations and 8km of 8.7m diameter bored tunnel between Issy-Vanves-Clamart and Villejuif-Louis-Aragon Stations employing two TBMs.

“We expect the first TBM for Line 15 South to start tunnelling by the end of this year,” said Baumont, “ and between 2019 and 2022 we will be working simultaneously on Line 15 South, Line 16, Line 17 and a part of Line 18. During this period will have 28 TBMs in operation at the same time and we will probably have backup TBMs at the ready.” Some sections of the new routes will be twin-bore, single-track running tunnels and others will be single-tube, double-track drives. TBMs in operation will be up to 10m in diameter and operation at between 30m and 50m below ground surface. The deepest station on the project will be built at 55m below ground level.

Pont de Bondy Station will use a bridge as a social space and cultural landmark

More detail about the Line 15 South project provides a better understanding of the vast amount of related project works. “This tunnel section in total will become 33km long,” said Baumont. “It will have eight access shafts and 16 underground stations progressing from 22 construction sites. That equates to one work site at about every 1,500m and about 38 associated works on the Line 15 South.” Baumont does not worry about the impact the simultaneous works will have on the city. “Practically 80% of the Grand Paris Metro is underground,” he said. However this does have some form of indirect impact on the adjoining neighbourhoods and local traffic, as the project will require a large fleet of trucks for the supply and evacuation of materials. “We will end up with more than 43 million tons of excavated material,” adds Baumont. “We are currently performing traffic studies to determine which routes our trucks need to take to minimise congestion.”

More complex are the station interfaces. Stations on the existing lines must remain fully operational during the expansion and connection works at the almost 60 stations that will provide transfer between the orbital and radial lines with some of the stations surrounded by a dense urban environment. Baumont takes the construction of a complicated station in the La Defense district as an example. “There are many roads, buildings and parks here and commercial centres with foundations of up to 40m underground. We will meet these foundations and have to come up with solid preparatory works to prevent issues.”

Grand Paris Express will stimulate urban development as here at the Saint Denis Pleyel Station

Perhaps the greatest challenge for the project is posed by the ground conditions. The Rivers Seine and Marne are to be crossed several times and boring underneath the western side of Paris will progress under a hill at the edge of the River Seine. “The ground here is unstable so we are currently trying to find solutions to help us build the stations safely. This will not involve grouting but we will put more concrete into the ground before we start construction.”

Radically different planning approach

Prepratory works, as well as station designs, are now well underway. All eight contracts for Line 15 South have been awarded (see separate news article in the References below). Advance of the project will continue with tendering of three civil construction contracts for the 26km long Line 16, which will include nine underground stations. The designs of the stations for Line 15 South and Line 16 are complete, station design for Line 17 is almost complete, and designs for Line 18 are at the halfway point.

When fully operational in what is expected to be 2030, the new system should serve the needs of the city for at least another 50 years. In terms of transport, as well as accommodating the future, the project is of a radically different approach than seen in other large metropolitan areas. Decisions were made not only to implement a project of this size, but also to add all new lines simultaneously. “By just adding a line, for example, every 10 years, we cannot cope anymore with the future,” explained Bas Bollinger, Global Leader Rail & Urban Transport at Arcadis.

“We have designed the metro system with a different mindset, opening up connections to such a large area in the central part of Paris that it will stimulate urban development everywhere,” he said. “Some medium densely populated areas have a lot of commuters who now work in downtown Paris. But based on the new orbital network a lot of these suburbs have started their own urban development program with more housing, shopping malls and other facilities that will attract more commercial activity and investment. This all boils down to the centre of Paris eventually multiplying in square meters.”