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A long steel structure with external ducts and pipes running horizontally along it.
An HS2 tunnel boring machine at the factory.

How HS2 build tunnels

Green tunnels

A green tunnel – or cut-and-cover tunnel  – is where a trench is excavated and roofed over, then the land on top of the tunnel is restored so it blends into the landscape. This technique will be used by HS2 for the following tunnels; Wendover in Buckinghamshire, Burton Green in the West Midlands, and Chipping Warden and Greatworth, both in  Northamptonshire. The tunnel at Long Itchington wood, in Warwickshire, will be built using both green tunnel and bored tunnel techniques.

Bored tunnels

A twin-bore tunnel is where two parallel tunnels, each containing a single rail track, are constructed using tunnel boring machines. The rotating cutter-head at the front of the TBM bores the tunnel. The TBM also installs the round concrete segments that form the tunnel walls.

Tunnel boring machines

Tunnel diameter

HS2 tunnels have large internal diameters. The trains will be travelling at high speed through the tunnels and larger tunnels help lower the pressure variations inside making it more comfortable for passengers.

Graphic illustration of the techniques described bellow.