Grimshaw unveils ‘landmark’ HS2 tunnel vent building

Grimshaw has revealed designs for a spiral steel vent shaft for a High Speed 2 tunnel in Buckinghamshire.The practice’s sculptural Amersham vent shaft headhouse stands in stark contrast to its four barn-like structures elsewhere on the 16km-long Chiltern Tunnel.The latest design is described as a spiral-shaped weathered steel wall, surrounding a conical headhouse with anodised aluminium fins.Set in the middle of a stretched roundabout just outside Amersham, the structure will provide ventilation and emergency access to the high-speed rail line where it disappears below the Chiltern Hills.Client HS2 Ltd said the building housing the vent shaft would be surrounded by a steel wall ‘designed to echo the shape of the site and the natural tones of the surrounding landscape’.To let light through, the upper parts of the wall will be lightly perforated with a pattern ‘inspired by woodland foliage’.A crown of aluminium fins on the headhouse itself will help disguise the shape of the building and soften views from afar.An 18m-deep ventilation shaft will reach down to the twin tunnels, with fans and other equipment designed to regulate air quality and temperature, remove smoke in the event of a fire and provide access for the emergency services.Grimshaw worked with High Speed 2 main works contractor Align JV – consisting of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick – on the project, as well as design partners Jacobs and Ingerop-Rendel, and landscape designers LDA Design.The plans for the headhouse are on public display, with local residents invited to attend a month-long virtual exhibition.HS2 Ltd engaged with the Chilterns Area of Outstanding Natural Beauty Review Group and Buckinghamshire Council during the development of the designs.