HS2s first images reveal the longest of the three ingenious tunnels which are set to be built through Buckinghamshire and Northamptonshire.
The cutting-edge ‘green tunnels’ will blend the high-speed railway line into the landscape and create less disruption for residents.
The innovative one and a half mile Greatworth tunnel will be manufactured in Derbyshire ahead of being transported to the location where it will be assembled over the railway line as it passes the village. The tunnel will then be covered with soil and landscaped so it blends into the countryside that surrounds it.
HS2’s main works contractor EKFB is made up of Eiffage, Kier, Ferrovial Construction and BAM Nuttall, will install the tunnel using an ‘off site’ approach following lessons learned from the construction of the latest French high-speed lines.
The tunnel is designed using an ‘m’ shaped double arch and will feature two independent halves for both southbound and northbound trains. As an alternative to the whole tunnel being cast on-site, five different precast concrete sections will be slotted together creating the double arch of one central pier, two side walls and two roof slabs. 5,400 Sections will be installed at Greatworth and will be steel-reinforced, the largest of which will weigh in at a huge 43 tonnes.
Concrete and steel create some of the largest carbon emissions in the construction industry and the use of this lighter weight, modular design is anticipated to reduce the amount of both materials by over half when compared to an embedded structure. The innovative new technique also needs fewer people and equipment on site which brings improvements in safety whilst lessening disruption for residents.
HS2 Ltd’s Project Client Rohan Perin, said:“The Greatworth green tunnel is a great example of what we’re doing to blend the new railway into the landscape and protect communities living close to the line. By adopting an ‘off site’ approach to manufacturing, we’re also cutting embedded carbon from the design, improving efficiency, safety and making the whole construction process less disruptive for the community.”
EKFB Delivery Director Andy Swift, said: “The green tunnel design is a combination of innovation, international engineering expertise and thoughtful landscaping for its local communities to enjoy. Once the tunnels have been built, the original earth removed from the cutting to make way for the tunnel, will be repositioned, creating a green space which will blend into the surrounding landscape.”
Structures similar to the Greatworth tunnel are also going to be built close to Wendover in Buckinghamshire and Chipping Warden in Northamptonshire and will see a combined total of four miles of tunnel. The tunnels will all feature specially designed ‘porous portals’ at both ends which will bring a reduction in noise when trains enter and exit the tunnels and small portal buildings which house safety and electrical equipment.
The project will see thousands of tonnes of rock and soil excavated through the primary stages of the construction and will be attentively separated and stored on-site where they will be reused further into the process and will support keeping lorries off of local roads.
Customised landscape design plans have also been created for each of the tunnels and will see thousands of native trees and shrubs in keeping with the local area such as Silver Birch, Oak, Beech and Willow planted to grow new areas of woodland around the portals and recreating the hedgerows and field boundaries over the tunnel.
The three tunnels will see each of the 13,290 sections made by Stanton Precast Ltd at their Ilkeston factory with the contract for the project creating around 100 jobs and has seen an increase in their workforce by approximately 50%. The project will see new production sheds, casting and storage areas built at the factory in order to house the new work.