Page 13 - TunnelTalk Annual Review 2017

Paris advancing its mega metro expansion
Paris has embarked on the largest underground project in the history of France. With about 170km of new underground infrastructure in total, the Grand Paris Express will expand the city’s metro system to one of the largest in the world. The project is of epic scale and will provide a multi- metro route solution to serve the rapid growth and increasing urban density of the city.
At the moment Paris has a radial mass transit network with commuters travelling from one suburb to another by taking a time consuming journey through the heart of the city. The new orbital network will connect suburbs to each other and carry passengers between 68 new stations, 51 of them connecting to the existing radial lines (Fig 1).
While the €25.9 billion orbital network will relieve 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 people needing to travel between suburbs,” explained Vincent Baumont, Deputy Director of the Mission of Project Management Consulting company Arcadis.
In addition, the Société du Grand Paris (SGP) wants also to maximise the benefits for the growing suburbs. “We will develop the property surrounding all new stations into lively neighbourhoods to support local economic growth,” said Baumont.
Construction of the Grand Paris Express started officially with a ground breaking ceremony for the Line 15 South project 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 southern edge of 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 north with the Charles de Gaulle Airport. 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.
Some sections of the new routes will be twin-bore, single-track running tunnels and others will be single-tube, double-track drives. TBMs of up to 10m in diameter will operate at between 30m and 50m below ground surface with the deepest station on the project at 55m.
Armand van Wijck, TunnelTalk Europe Correspondent
The first construction phase 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,” said Baumont.
Total value of civil contracts on the Line 15 South project, linking Pont-de- Sèvres to Noisy-Champs is €3.7 billion (Fig 2 and Table 1).
By the end of 2017, the first of 10 TBMs to be used on the project will have started excavation. “Between 2019 and 2022 we will be working simultaneously on Line 15 South, Line 16, Line 17 and a part of Line 18,” said Baumont. “During this period we will have 28 TBMs in operation at the same time and more TBMs at the ready. The project will require a large fleet of trucks for the supply of the materials to the construction sites and the removal of muck. “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 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.”
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.”
All eight contracts for Line 15 South have been awarded (Table 1) and the project will continue with tendering of three civil construction contracts for the 26km long Line16,whichwillincludenineunderground 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.
Faced with annual financing needs, which will reach €2 billion per year by 2018, the Supervisory Board of the Société du Grand Paris secured a second €1 billion loan
from the European Investment Bank (EIB). This adds to the €1 billion loan agreed with the Caisse des Dépots savings fund in July 2015 and a similar contract for another €1 billion with the EIB secured in April 2016.
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
Fig 1. The four new metro lines and extensions
Table 1. Scope and construction schedule
Line
Length
Stations
Year of operation
15
75km
37
2030
(south section 2022)
16
26km
10
2023
17
28km
9
2030
18
35km
11
2030
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