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Tunnels

HS2 will dig 64 miles of tunnels between London and the West Midlands alone.

An aerial picture of tunnel boring machines sitting in a cutting.
An image captures the scale of the work at the South portal tunnelling site.

Launching HS2’s first TBM

HS2 Ltd has announced the launch of the first tunnelling boring machine (TBM), the TBM Florence from HS2’s South Portal site next to the M25 in Buckinghamshire.

Find out more about the launch.

How HS2 build tunnels

HS2’s tunnels will be built using different construction techniques to suit their purpose and local conditions. We’re building them under cities and the countryside to help reduce the impact on people and nature.

Green tunnels

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

Bored tunnels

A twin-bore tunnel is where 2 parallel tunnels, each containing a single rail track, are constructed using TBMs. 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 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.

Tunnel boring machines

Ten giant tunnel boring machines (TBMs) will dig 64 miles of tunnels between London and the West Midlands.

Each machine operates as a self-contained underground factory – digging the tunnel, lining it with concrete wall segments and grouting them into place at a speed of around 15 meters a day.

Find out more about our giant tunnel boring machines

HS2 will dig over 80 miles of tunnels, forming part of the HS2 network that will help connect the country, create thousands of jobs and rebalance the UK economy.

The longest and deepest tunnel will be the Chiltern tunnel measuring at 10 miles (16km) long and will go as deep as 90 metres.

The London tunnels are 13 miles (21km), with a maximum depth of 50 metres. There will also be tunnels in the West Midlands, Buckinghamshire and Warwickshire and Northamptonshire.

In total 130 million tonnes of earth will be excavated, enough to fill Wembley Stadium 15 times!