HS2’s Long Itchington Wood Tunnel north portal
One of HS2’s largest construction sites in the Midlands is being prepared for the launch of a tunnel boring machine (TBM) that will dig a one-mile long twin bore tunnel under Long Itchington Wood, before it heads north towards Birmingham Curzon station.
The site is managed by the BBV Joint Venture (Balfour Beatty Group and Vinci Construction). There are currently 60 workers on site including student engineers and apprentices. Twenty students from Walsall College will complete their 45-day T-Level industry placement with BBV working on the delivery of HS2. Current work on the 1km sq site entails a large and deep excavation, with 250,000m3 of material being excavated in layers before being transported and deposited locally to form environmental embankments for the main line.
The 2,000 tonne tunnel boring machine, which has been manufactured in Germany by Herrenknecht, is due for delivery on site in early 2021, will be launched in Summer 2021 and completion of the boring will be mid-2022. The tunnel will be around 9m-10m in diameter.
The TBM will take about five months to complete the first bore of the twin bore tunnel. Once the first bore is complete, the TBM will be extracted at the south portal reception box before being transported by road back to the north portal to commence the second bore. A large portion of the TBM support modules will be drawn back through the bored tunnel before being positioned on the cradle for the second bore.
Work on a green tunnel located south of the south portal will commence later this year using the D-Wall rigs mobilised for the reception box. Excavation of the reception box will be undertaken in this period with the material being stockpiled locally.
On this stretch of the route there are two tunnels being built by BBV – the other one is Bromford Tunnel. There are also 100 bridges, 35 viaducts, 36 cuttings and 70 bridge structures.
Michael Dyke, managing director of Balfour Beatty Vinci said: “In readiness for the arrival of the first tunnel boring machine, works have already commenced in earnest to prepare the Long Itchington Wood Tunnel north portal site, with our expert team and valued supply chain partners excavating 250,000m3 of material before reusing it elsewhere across the route. Critical to the successful delivery of Europe’s largest infrastructure project – HS2 - the 2,000 tonne tunnel boring machine will set off on its journey from the portal next summer, travelling from north to south to create the twin bore Long Itchington Wood Tunnel.”
David Bennett, HS2’s delivery director said: “The Long Itchington Wood Tunnel north portal site is a key site on the Midlands section of the HS2 route, and it’s great to see work progressing well in preparation for the arrival of the tunnel boring machine next year. The tunnel in this location goes under Long Itchington Wood specifically to preserve a section of ancient woodland. This forms a key element in how we are managing environmental impacts through the design of the railway. Along with 32 miles of tunnel, HS2 will also be criss-crossed by over 150 bridges and underpasses on Phase One, including 16 specially designed ‘green bridges’ covered in planting, and a green corridor alongside the route will integrate HS2 into the landscape.”
Derbyshire-based Collins Earthworks is undertaking bulk earthmoving on the project, while SB3, a joint venture between Soletanche Bachy and Balfour Beatty Ground Engineering, are undertaking the soil nailing and shotcrete at the north portal plus the D-walls, secant piles and slurry walls at the south portal.
Welcoming the news, HS2 Ltd Chief Executive Mark Thurston said: "The launch of our first tunnelling machines will be a defining moment in the history of HS2 - and our work to deliver a high speed railway that will offer a low-carbon alternative for journeys across the UK. Construction is now well underway, with more than 13,000 jobs supported by the project, both directly and in our UK-wide supply chain. The arrival of Florence and Cecilia is a major step forward and our expert team will now work to assemble, test and commission them before their launch next year."
Designed specifically for the mix of chalk and flints under the Chilterns, the two identical TBMs will dig separate tunnels for north and southbound trains, with Florence set to launch first and Cecilia to follow a few weeks behind. Each machine operates as a self-contained underground factory, which as well as digging the tunnel, will also line it with concrete wall segments and grout them into place as it moves forward at a speed of 15 meters a day. Each tunnel will require 56,000 segments - which will all be made on site.
A crew of 17 people will operate each TBM, working in shifts to keep the machines running 24/7. They will be supported by over 100 people on the surface, managing the logistics and maintaining the smooth progress of the tunnelling operation. These first two TBMs will be operated by HS2's main works contractor, Align - a joint venture formed of three international infrastructure companies: Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick.
(Work going on at the tunnels' South Portal)
Align Project Director Daniel Altier commented: "Now that the parts have arrived the detailed job of assembling and commissioning the machines has begun.
"There are also considerable other activities continuing on our site to prepare for the launch of Florence and Cecilia next year. This includes the construction of a factory that will manufacture the concrete segments to be used to line the tunnel and a slurry treatment plant that will process material from the tunnels."
The Align Joint Venture expects to recruit 1,200 vacancies, with over 100 opportunities for apprentices. They plan to target their recruitment and investment in upskilling local people who are currently unemployed, with a particular focus on women, under 25s and those with disabilities. This is another great example of the vital role HS2 continues to play in the UK Government's Plan for Jobs to protect, support and create employment, which has helped millions of people to continue to provide for their families over the past eight months of the COVID-19 crisis.
Built by Herrenknecht, a world leader in TBM manufacturing, at its factory in south-west Germany, the two 170m long machines were transported to the UK in more than 300 separate shipments over the course of two months, with the parts now safely delivered to the Align Chiltern tunnel site, to the west of London just inside the M25.
The names of the two TBMs were suggested by students at Meadow High School in Hillingdon and The Chalfonts Community College, Buckinghamshire, which are close to the tunnel launch site. They were inspired by Florence Nightingale, the founder of modern medicine, and pioneering astronomer and astrophysicist, Cecilia Payne-Gaposchkin.
Around 4,500 people from across the UK took part in the poll to select the final names, with Florence taking 40% of the vote and Cecilia a close second with 32%.