HS2 is one of the most expensive rail projects in the world, and has been under construction for more than three years, although no trains are expected to run on it until at least 2029. Despite the recent announcement that the northern legs of the rail link have been scrapped, work across a vast swathe of southern England and the Midlands continues. Drills are churning under the landscape between London and Birmingham around the clock, with 350 active construction sites along the 140 mile (225km) route.
Eleven tunnels, a viaduct that will be the UK’s longest railway bridge, and four new stations are all planned, with the track itself being laid later. The vast system of tunnels being created to let HS2 trains pass through most of the countryside below ground is one of the most time-consuming and expensive parts of the project. Of the proposed 32.5 miles (52.5 km) of tunnels, approximately 14 miles (22.5km) have already been completed, including about 75% of the 10-mile (16km)-long Chiltern tunnel. The South entrance of said tunnel is located near the West Hyde village in Hertfordshire.
A fleet of giant tunnel-boring machines, some up to 560ft (170m) long, are used to cut through the earth and rock with rotating cutterheads, while soil is funnelled away behind. As the machine advances, it also lays concrete segments, forming the ring of the tunnel. The tunnels are about 30ft (9m) wide, and up to 300ft below the surface in some places. The machines, which all have female names such as Caroline and Sushila, work 24×7 and cut through about 50ft (15m) a day.
Some of the
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