HS2 has revealed the Chiltern Tunnel north portal designs, which is designed to be noise cancelling, to cut noise from trains entering and exiting the tunnel at speeds of up to 320km/h
The Chiltern Tunnel north portal design will incorporate two perforated concrete hoods, which will cover the track and extend the 10 mile long tunnel into the open air.
The ‘porous portals’ will avoid sudden changes in air pressure and resulting noise caused by trains entering and exiting the tunnels.
Set low into the landscape between Great Missenden and South Heath in Buckinghamshire, the portals will only be visible from a footbridge over the railway to the north.
To allow for the different levels of air pressure, the portal for trains entering the tunnel will be 220m long, while the one for those exiting will be just 135m. Both will have smooth concrete on top and textured concrete to a low level, to reduce staining and maintenance.
The Chiltern Tunnel north portal design will also feature a simple single-storey ancillary building to house mechanical and electrical equipment.
HS2 are currently seeking views from the community about the final design, with options including a green roof, split louvred or anodised aluminium façade.
The tunnel design will play a crucial role in reducing noise caused by the high speed train
HS2 Ltd’s project client, David Emms said: “Once construction is complete, the Chiltern tunnel will take HS2 trains deep under the Chiltern hills, linking London with Birmingham and the North and releasing space for more freight and local services on the existing mainline.
“Set low into the landscape and out of sight for most passers-by, the structures will play a crucial role in cutting out unnecessary noise and housing essential mechanical and electrical equipment.
“We are keen to hear local views and I would encourage people living locally to have a look at the designs and let us know what they think.”
The structures have been designed and will be built by HS2 Ltd’s main works contractor Align JV.
Work is underway on the tunnel, with two enormous 2,000 tonnes tunnel boring machines heading north from the south portal to excavate the twin-bore tunnels.
To the north of the Chiltern Tunnel, the new high speed line will be set into a cutting for 1.8 miles (3km) on its approach to the Wendover Dean Viaduct, with more than 20 hectares of new woodland, shrubs and wildflowers planted to help blend the railway into the surrounding countryside.
Across this stretch of the line, six new bridges will cross the railway cutting, linking country lanes and historic footpaths to the east and west.
The surface route to the north of the tunnels is being built by another of HS2’s main works contracts EKFB.
