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Laigh Milton Viaduct is a railway viaduct near Laigh Milton mill to the west of Gatehead in East Ayrshire, Scotland, about 5 miles (8 km) west of Kilmarnock. It is probably the world's earliest surviving railway viaduct on a public railway,〔Roland Paxton and Jim Shipway, ''Civil Engineering Heritage: Scotland Lowlands and Borders'', Thomas Telford Publishing, London, 2007, ISBN 978-0-7277-3487-7.〕 and the earliest known survivor of a type of multi-span railway structure subsequently adopted universally.〔 The viaduct was restored in 1995-96〔and is a Category A listed structure since 1982.〔Engineering Timelines, at ()〕 It bridges the River Irvine which forms the boundary between East Ayrshire and South Ayrshire. It was built for the Kilmarnock and Troon Railway, opened in 1812; the line was a horse drawn plateway (although locomotive traction was tried later). The first viaduct was closed in 1846 when the railway line was realigned to ease the sharp curve for locomotive operation, and a wooden bridge was built a little to the south to carry the realigned route. This was in turn replaced by a third structure further south again, which carries trains at the present day. ==The first Laigh Milton viaduct == The first viaduct was constructed as part of the Kilmarnock and Troon Railway, which opened on 6 July 1812. It is located at National Grid Reference NS 3834 3690. It was built with four segmental arches of 12.3 m (40 feet) span, and a rise of one-third span; the voussoirs were 610 mm (24 inches) thick. The railway was carried about 8 m (25 feet) above the river surface.〔 The arches were of local freestone with sandstone ashlar facings and rounded cutwaters: these were later extended to form semi-circular buttresses. Built in 1811 - 1812, it is the oldest surviving railway viaduct in Scotland.〔 and one of the oldest in the world. It is about 82 m (270 ft) long by 5.8 m (19 ft) wide over all. The piers are 9 ft (2.7 m) wide. Photographs taken prior to the recent restoration show the viaduct without parapets, and there is no evidence that these were provided.〔''Laigh Milton Mill, Railway Viaduct'', on the website of the Royal Commission on the Ancient and Historical Monuments of Scotland, at ()〕 The engineer for the whole line was William Jessop, and the resident engineer was Thomas Hollis, and he was probably allowed considerable autonomy by Jessop. The stonemason was probably John Simpson, who had been extensively employed by Jessop at Ardrossan and on the Caledonian Canal.〔R A Paxton, ''Conservation of Laigh Milton Viaduct, Ayrshire'', Proceedings of the Institution of Civil Engineers, Volume 126, London, 1998〕 Hollis was refused permission to dismantle part of the mill dam to lower water level for pier construction, and "in July 1809 he was authorized to proceed by means of a cofferdam, involving 'very little more expense', with the advantage that 'the stones for the bridge can be floated down on a punt'.〔''Kilmarnock and Troon Minute Book'', quoted in Paxton (ICE)〕 Paxton suggests that the original standard of construction was poor: This utilitarian, medium-scale viaduct was designed in accordance with traditional rather than 1810 state-of-the-art practice. It did not incorporate the hollow cross-tied spandrel improvement then being adopted with increasing frequency by leading engineers. If this had been adopted here instead of clay fill, it would have obviated the spandrel bulging and some of the stone loss that occurred. Much of the viaduct's stone quality and some workmanship at the west end were only just adequate for the purpose ... but the flat-stone, lime-mortar-bedded, pier hearting carried up to 1.5 m above arch springing was an effective feature which had probably saved the piers from collapse. In cross-section, the spandrels presented an unusual application of the classic gravity retaining wall.〔 In the later decades of the twentieth century the viaduct had fallen into an ever-worsening condition, with much serious erosion and loss of facings; the western arch had sagged and the second arch had hogged; cracks up to 60 mm had opened up in the extrados of the arch rings. It had become obvious that the structure was near to collapse, and in February 1992 the Laigh Milton Viaduct Conservation Project was formed.〔 It is described below. When it was by-passed, it remained in place, and was used as a footway and possibly for cartage to and from the pit on the west side of the river, Fairlie Colliery No. 3. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Laigh Milton Viaduct」の詳細全文を読む スポンサード リンク
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