Chiltern Tunnel portals designed to reduce noise levels
HS2 Ltd has revealed the design for the north portals of Chiltern Tunnel, with the intention of reducing the level of noise from trains entering and leaving at speeds of up to 320kph (200mph).
Two perforated concrete hoods will cover the tracks and extend the ten-mile-long twin-bore tunnel into the open air by up to 220 metres for trains entering the tunnel and 135 metres for those exiting.
Both extended portals will have a smooth concrete top and textured concrete to a low level, which will be porous to avoid sudden changes in air pressure from moving trains.
Set into the landscape between
Great Missenden and South Heath in Buckinghamshire, the portals should only be visible from a footbridge crossing the railway to the north.
Alongside the portals, a single-storey ancillary building is also due to be built by main works contractor Align JV (comprising Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick) to house mechanical and electrical equipment.
HS2 is currently consulting with the local community about the final design, with options including a green roof, split louvred or anodised aluminium facade.
“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 main line,” said HS2 Project Client David Emms.
“Set low into the landscape and out of sight for most passers-by, the structures will play a crucial role in cutting 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.”
Excavation of Chiltern Tunnel is now well under way, with two 2,000-tonne tunnel boring machines having now reached Chalfont St Peter from the south portal (more than 3km). Breakthrough at the north portal is expected in two years’ time.
The north portal also marks the transition point between main construction by the Align JV and EKFB (comprising Eiffage, Kier, Ferrovial Construction and BAM Nuttall).