Greatworth tunnel
The longest green tunnel
Greatworth tunnel is the longest green tunnel on the HS2 route. It will stretch for 1.7 miles (2.7km) through West Northamptonshire.
It is one of five cut-and-cover, or green tunnels, on the route. These tunnels are built on the surface before being buried. We then place trees, plants, and shrubs on top to blend the tunnel into the landscape. Material from the excavation is kept on site and reused on the tunnel surroundings. This reduces the number of trucks on the road.
Tunnel construction
Unlike a bored tunnel, the tunnel is being built using a ‘cut and cover’ process. This involves excavating a cutting, building the tunnel, and then burying it, with trees, shrubs and hedgerows planted on top to blend in with the surrounding countryside.
The construction of the tunnel is happening in stages, with the cutting first being excavated and then a layer of ‘blinding’ laid to form a concrete base for the structure. To speed up the blinding process, the steel reinforcing bars are now being delivered as a ‘roll mat’ with the parallel bars connected by mild steel tape so they can be quickly rolled out ready for the concrete pour.
M-shaped double arch
Designed as an m-shaped double arch, the tunnel will have separate tunnels for southbound and northbound trains. Instead of casting the whole tunnel on site, five different concrete precast segments are slotted together to achieve the double arch – one central pier, two side walls and two roof slabs. There are 5,020 steel reinforced segments.
Similar green tunnels are being built at nearby Chipping Warden, as well as Wendover in Buckinghamshire and Burton Green in Warwickshire, stretching for a combined total of more than four miles. The tunnels will all have porous portals at either end to reduce the noise of trains as they enter and exit the tunnel. There are also small portal buildings that contain safety and electrical equipment.
Landscaping design plans
Landscaping designs include thousands of native trees and shrubs typical to the local area – including silver birch, oak, beech and willow – planted to create new woodland areas around the portals and recreate the hedgerows and field boundaries on top of the tunnel.
Slide 1 of 3: Greatworth Green Tunnel portal view 1
Slide 2 of 3: Greatworth Green Tunnel portal view 2
Slide 3 of 3: Greatworth Green Tunnel portal view 3
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