Almond Valley Viaduct
Newbridge, Edinburgh, Scotland, UK
September 1839 - May 1841
Railway Viaduct |
ICE reference number
Almond Valley Viaduct — also known as Ratho Viaduct — is the longest structure on the Edinburgh & Glasgow Railway. Construction was completed in 1841 but strengthening works have enabled it to remain in service on the modern inter-city express line.
The massive viaduct was designed by John Miller (1805-83) as part of the high-speed trunk line constructed between the cities of Edinburgh and Glasgow (built 1838-42). The contractor was leading bridge builder John Gibb (1776-1850) of Aberdeen, who also built the Winchburgh Tunnel and cutting.
Gibb's combined estimate for Almond Valley Viaduct and Winchburgh Tunnel contained a mistake, which was carried through to the contract. Alhough he discovered the error before his tender was accepted, he felt bound to honour the original sum, resulting in a personal loss of £40,000.
The viaduct is in two sections, separated by a high embankment some 400m long. The eastern section comprises 36 ashlar-faced segmental masonry arches each of 15.2m span, and up to 21.3m high. It crosses the Almond Valley in a wide sweeping curve of about 2.4km radius.
The western section has seven arches, the central and largest of which bridges the Edinburgh to Bathgate road (A898). It has a span of 20.1m, with three arches of 15.2m span on either side.
It cost £130,000 to construct and opened to rail traffic on 18th February 1842.
Modern trains are heavier and travel faster than those the structure was designed to carry. This led to a series of strengthening works. In the 1950s, the hollow piers and arches on the eastern section were filled with concrete. The arches were strengthened with steel spandrel ties to the arch rings.
The central arch of the western section was badly affected by settlement caused by past local shale oil workings. It was strengthened with brick cladding on the existing masonry piers, by the insertion of a steel truss under the affected arch and by tie rods through the truss to the arch haunches. Brick infilling to prevent distortion was used to strengthen the other six arches.
In 1988, the piers and arches had been strengthened further — at the arch rings using steel bands made from old rails.
Although the various remedial works may be thought unsightly, Almond Valley Viaduct is still serving the main line between Edinburgh and Glasgow after 164 years. It has been a Category A listed structure since February 1971.
Contractor: John Gibb & Son (Aberdeen)