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High Speed | Systra: Driving innovation on Tours-Bordeaux

Most new rail projects require innovation and adaptation; the South Europe Atlantic (SEA) high speed line being constructed between Tours and Bordeaux impresses with the sheer number and scale of inventive ideas.

The SEA line, is an important part of France’s burgeoning high-speed network, it will provide a two hour journey time from Paris to Bordeaux, a saving of around one hour, and will further reduce journey times to Toulouse and to Spain. As well as around 300km of high-speed line, the project includes 40km of standard railway, linking to existing lines, and hundreds of bridges and structures. 

The concession awarded by French rail infrastructure manager SNCF Réseau is an unusual one: 50-years long with some of the most stringent availability targets ever seen. Global availability must be 99.98% which equates to less than 120 minutes of unavailability per year. 

French high speed line

French high speed line

Concessionaire Lisea, made up of Vinci and infrastructure investment funds, will provide half of the €7.8bn (£6.15bn) capital cost and collect a return on its investment via tolls. Lisea awarded the design-construction and the maintenance to joint venture organisations named Cosea and Mesea respectively.

“Perhaps the strongest message from our SEA experience is that the form of procurement absolutely drives innovation,” says Systra Engineering director, UK Steve Higham.  The new line is expected to bring economic and environmental benefits to towns along its route. As well as moving traffic from road to rail, reducing congestion and pollution, SEA will also free up capacity on existing lines for passenger and freight services.

The terms of the concession have led to a design ethos which looks to optimise the system, breeding a raft of innovations which have reduced construction and future maintenance costs, some of which are detailed below.

Logistics

The design team re-thought track bed construction to introduce a 140mm-thick layer of asphalt below the ballast. As well as reducing the depth of track bed by 25% this has allowed the line itself to be used as a haul road and logistics artery, reducing the need for extra service infrastructure only required for the construction phase. This has kept the impact of construction traffic using the existing road networks to a minimum. 

Two logistics centres, managed by Systra, serve the whole 300km length, with road vehicles rather than rail ones used to install the overhead lines and ballast. Rates such as 20 overhead line masts erected per team per day are achieved consistently on the project, far higher than those achieved with conventional rail plant.

Reduced maintenance

The 250 bridges that cross over the new line have been designed so that there are no bearings on the piers next to the high speed line. Each one has been built using the same system: a pre-cast concrete “kit of parts”, all fabricated off site.

Standardisation

Standardisation and offsite manufacture have delivered huge time savings in the construction of seven major viaducts along SEA’s route. Using over 400 standardised post-tensioned concrete box sections, Cosea has constructed each bridge deck in just two months.  

Extreme weather

Since 2012, Systra has undertaken a global study for the International Union of Railways on the impacts of natural disasters and extreme weather on high-speed and intercity lines. This has led to mitigation solutions, for example to tackle the problem of strong wind, new track protection and on-board automatic speed restriction systems have been developed. 

Acoustics

To limit viaduct acoustic impact, Systra has been developing solutions to reduce noise directly at source. The aim is to develop an acoustic system completely integrated to the viaduct, while preserving the architectural qualities.

Station architecture

Systra’s experts in station architecture have been enhancing passenger’s experience behind the scenes for many years, developing solutions to increase natural light, heating, ventilation and acoustics as well as passenger flow and experience.

Produced in association with

Systra

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