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HS2 makes good progress on Chilterns tunnel

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HS2 makes good progress on Chilterns tunnel
Inside the Chilterns tunnel.

The first bore of HS2’s Chiltern tunnel has reached the one-mile mark, or around 10 per cent of the way through from its starting point just inside the M25.

Florence, the leading 2,000-tonne tunnel boring machine (TBM), launched in May. The 170-metre-long machine, basically a self-contained tunnelling factory, is cutting its way through a mix of chalk and flint beneath the Chiltern hills in Buckinghamshire and turning the spoil into a slurry which is pumped out to the surface.  There, it will be dried out and used both to landscape the project and provide fill for other works.

Video flythrough of the first mile of HS2’s Chilterns tunnel.

As the TBM cuts its way through the rock, it lines the tunnel with concrete segments and grouts them into place.

Florence isn’t making the journey alone. Her sister TBM Cecilia is running alongside and slightly behind her, cutting the second bore of the twin tunnels.

Concrete tunnel-lining segments being delivered to the TBM.

The two TBMs are operated by HS2’s main works contractor, Align – a joint venture formed of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick. A crew of 17 people keep the machines running, working in shifts and supported by over 100 people on the surface, managing the logistics and maintaining the smooth progress of the tunnelling operation.

Rohan Perin, HS2

Commenting on the progress so far, HS2 project client Rohan Perin said: “The 10-mile Chiltern tunnel will take HS2 underneath the hills and safeguard the woodlands and wildlife habits above ground as well as significantly reducing disruption to communities during construction and operation of the new railway.

“Once complete, HS2 will offer low carbon journey options linking London with the major cities of the north and releasing capacity for more freight and local trains on our existing mainlines. It’s great to see how much progress has been made over the summer and I’d like to thank the crew of Florence and all the tunnelling team for their hard work.”

Facts and figures

Each of the separate northbound and southbound tunnels will require 56,000 precision engineered, fibre-reinforced concrete wall segments – which are all being made at the south portal of the tunnel, next to the M25. During her first mile, Florence and her crew have installed more than 5,500 separate segments, each weighing around 8.5 tonnes.

Approximately 2.7 million cubic metres of material will be excavated during the construction of the tunnels and used for landscaping around the south portal site. Once construction is complete, this will help create around 90 hectares of wildlife-rich chalk grassland habitats. Chalk grassland used to be widespread across the hills of south east England and are considered habitat of international conservation significance with just 700ha left across the Chilterns.

In total there will be ten TBMs on the HS2 project – working to create 64 miles of tunnel between London and the West Midlands including major tunnels on the approach to London and Birmingham.

More than 20,000 jobs and over 650 apprenticeships are already being supported by HS2, which is set to transform transport links between Britain’s major cities, free up space on the rail network for more freight and local services and support the UK’s transition to net zero carbon emissions.

The TBM is named after Florence Nightingale, the founder of modern nursing, who spent many years in Claydon, Buckinghamshire, where she wrote books on nursing. The name was suggested by students at Meadow High School in Hillingdon.

Cecilia is named after Cecilia Payne-Gaposchkin, the astronomer and astrophysicist, born in Buckinghamshire, who attended Cambridge University before becoming chair of Astronomy at Harvard University in the United States. The first person to properly ‘read’ a temperature on stars, she also discovered that stars are made mainly from hydrogen and helium. Cecilia’s name was suggested by students at The Chalfonts Community College in Buckinghamshire.

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