Six Vent Shafts above Chipping Sodbury Tunnel (SWB10264)

Summary

Six tunnel vent shafts in a castellated style, built c.1897-1903.

Reasons for Designation

The Six Ventilation Shafts above Sodbury Tunnel are designated at Grade II for the following principal reasons:
* Architectural interest: the unified and characterful design of battered shafts and battlemented parapets is a result of a skilful sympathy to the surrounding historic landscape;
* Engineering interest: the vents illustrate the considerable engineering achievement of a tunnel of 2.5 miles in length;
* Group value: there is clear interest in the inter-related grouping of the designated tunnel mouths and the six ventilation towers, and their relationship to the wider context of their historic architectural and landscape setting.

History

South Wales & Bristol Direct Line

The Great Western Railway (GWR) line from London to Bristol was built in 1835-41. It was always envisaged that it would connect with a line to South Wales, providing a link to Fishguard and Ireland. However the route to Wales was at first an awkward one, either (from 1852) circuitously via Gloucester or by train and ferry from New Passage, north of Bristol. The construction of the Severn Tunnel in 1876-83 transformed the rail connection to Wales for both passenger and freight (especially coal) traffic. However to reach the tunnel trains still had to go via Bath and Bristol, making the distance from London to Cardiff 155 miles. The decision was taken in 1896 to shorten that route by creating a direct 30 mile link from Wootton Bassett to Patchway. This reduced the distance to Wales by 10 miles and avoided the congestion and slow running in and around Bristol. The line was built 1897-1903, and was one of the most important of a number of improvements to long distance routes made by the GWR at that time.

Chipping Sodbury Tunnel

The bridges and other structures along this line were built to more standardised designs than characterised the engineering of earlier parts of the GWR network, especially in the use of brick segmental arched bridges, of single- or triple-span. The tunnel portals, and even more the tunnel vent shafts, were more distinctive, perhaps in recognition of their role in the landscape. It is not known who was directly responsible for their design, but Sir J.C. Inglis (1851-1911), later General Manager of the GWR, was the principal engineer of the new route.

The Cotswold Edge escarpment was the largest topographical impediment to a direct, fast route. It was overcome by boring the Chipping Sodbury Tunnel. At 2.5 miles, it is the longest tunnel on the line, and passes under the Badminton Estate. It was one of the last major mainline railway tunnels to be built in the UK until the Channel Tunnel Rail Link opened in 2003.

Six shafts were dug down to the tunnel bore. These had two purposes. First, access for construction and removal of spoil. Second, to allow steam and smoke from steam locomotives to escape. Each of these shafts is crowned with a ‘chimney’, to prevent anything falling into shaft, which are strung out in a line in the fields above the tunnel.

The shafts were constructed on the Badminton estate, only 1.5 to 3 miles from Badminton House. Consequently they were designed to look like small castellated towers or turrets. This idea, derived from the English landscape tradition for objects of interest or follies, had been used to disguise shaft-heads to mines and tunnels since the C18.

Details

MATERIALS: GWR contrasting red and purple engineering brick and stone dressings.

DESCRIPTION: six circular, battered shafts, constructed of engineering brick laid in English bond, with machicolations and castellated parapet. The stepped machicolation corbels and the steeply pitched coping are stone. The shafts vary in height from c. 4 to c. 8m.

The shafts rise from a pastoral landscape. Each adjoins a spoil heap, sometimes with a levelled top and the alignment of a tramway along which trucks carrying spoil were wheeled away from the shafthead.

Sources

Books and journals
Cross-Rudkin, P, Chrimes, M, EDS, Biographical Dictionary of Civil Engineers Volume 2: 1830–1890, (2008)
MacDermot, E T, A History of the Great Western Railway, (1927, revised ed. 1964)
Vaughan, A, A Pictorial Record of Great Western Architecture, (1977)

Other
Alan Baxter & Associates, The History and Significance of the Great Western Main Line , 2012,

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