Chipping Sodbury Tunnel West Portal (SWB10348)

Summary

Tunnel portal in a classical style with a horseshoe arch erected c. 1897-1903 at the end of a cutting in a hillside.

Reasons for Designation

The West Portal of Chipping Sodbury Tunnel is designated at Grade II for the following principal reasons:
* Architectural interest: the survival of a group of two tunnel portals and their six, related tunnel vents and their shared aesthetic;
* Design, Engineering and Material Interest: the quality and strength of the design, its sympathy to the surrounding landscape and the fact that the visible parts of the tunnel symbolise 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 tunnel mouths and the six ventilation towers, and their relationship to the wider context of their historic architectural and landscape setting.

History

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.

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.

Details

MATERIALS: all squared and coursed quarry-faced sandstone except the engineering brick arch ring.

DESCRIPTION: horseshoe tunnel mouth with moulded engineering brick arch, including outer roll, and giant key stone, flanked by emphatic raked piers treated as broad pilasters, which project above the parapet. Straight wing walls outside the piers. Across the whole elevation, triple-stepped cornice and projecting coping, which form part of a central parapet projection which rests on the keystone.

The portal is set into a hillside just below the village of Old Sodbury, which forms the backdrop when the tunnel is viewed from the overbridge a few hundred metres down the line to the west. One of the tunnel's castellated vents can also be seen from here on the crest of the hill which rises up behind the village.

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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