The Crueize viaduct is a railway viaduct on the Béziers to Neussargues line, located in the commune of

Saint-Léger-de-Peyre Saint-Léger-de-Peyre (; ) is a commune in the Lozère department in southern France. Geography The river Colagne flows southwestward through the southern part of the commune and crosses the village. See also *Communes of the Lozère departme ...

, in the

Lozère Lozère (; ) is a landlocked Departments of France, department in the Regions of France, region of Occitania (administrative region), Occitanie in Southern France, located near the Massif Central, bounded to the northeast by Haute-Loire, to the ...

département of

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

. It is nicknamed the "Viaduc de l'Enfer" after the

valley A valley is an elongated low area often running between hills or mountains and typically containing a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over ...

it crosses. Built by the French government under the direction of Léon Boyer, it was commissioned in 1887 by the Compagnie des chemins de fer du Midi et du Canal latéral à la Garonne (C^ie du Midi), the concession holder for the line and viaduct. It should not be confused with the Crueize road bridge.

Location

At an altitude of 905 metres, the Crueize viaduct is located at

kilometric point A milestone is a numbered marker placed on a route such as a road, railway line, canal or boundary. They can indicate the distance to towns, cities, and other places or landmarks like mileage signs; or they can give their position on the ...

(KP) 629.723 on the Béziers to Neussargues line, between the Marvejols and Saint-Sauveur-de-Peyre stations (the latter currently closed). It is flanked by the Lestoura tunnel at KP 628.977 and the Born tunnel at KP 634.564.

History

Marvejols to Neussargues section, where the Crueize viaduct is located, is a textbook case for successful route selection in a difficult environment, due to steep-sided valleys. The initial studies, carried out by engineers from the French government, concluded that the route should be a conventional one through the valleys, and this project was validated shortly before the arrival of the young engineer Léon Boyer, who was put in charge of this section. LeonBoyer

He resumed the studies, proposing a route over the top of the plateau, which offered the advantage of avoiding a multitude of secondary structures and limiting the number to a few major or even exceptional ones. The difference in cost is significant, since the initial estimate was 9,500,000

franc The franc is any of various units of currency. One franc is typically divided into 100 centimes. The name is said to derive from the Latin inscription ''francorum rex'' (King of the Franks) used on early French coins and until the 18th century ...

s, whereas it was reduced to 6,500,000 francs in Léon Boyer's project. The revised project also makes for an easier line profile (less gradient), with the track remaining on a relatively flat plateau. Léon Boyer undertook the study of the line and the design of its many engineering structures. The most remarkable of these are the Garabit and Crueize viaducts, as well as the Chanteperdrix, Sénouard and Piou viaducts. On the Crueize project, he directed the work with the support of his chief engineer Charles Bauby. In May 1879, the Ministry of Public Works published an announcement in the ''

Journal officiel de la République française The ''Official Journal of the French Republic'' (), also known as the ''JORF'' or ''JO'', is the government gazette of the French Republic. It publishes the major legal official information from the national Government of France, the French Pa ...

'' (Official Journal of the French Republic) calling for the adjudication of works to be carried out on the railway from Marvejols to Neussargues. This involved the 4th construction lot, between KP 8.400 and 11.290, over a length of 2,890.50 m, with the main structure being the "Crueize viaduct", with 216 m long and 63.20 m high. The total cost of the project, excluding contingencies, was estimated at 2,717,203.08 francs at the time. Following the tender, the viaduct construction site was opened in early 1880. During 1882, work progressed rapidly. In August 1884, the engineering structures were completed and the company began laying the track for the section. The viaduct was put into service on May 9, 1887, when the Compagnie des chemins de fer du Midi et du Canal latéral à la Garonne opened the Marvejols to Saint-Chély section.

Characteristics

General description

The viaduct is set in the Crueize valley, in a steep, wild spot known as the "

gorge de l'Enfer A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency to ...

". Le viaduc de Grueize, Charles Talansier, 1891, p. 145. It has a slightly pinkish hue, with slender piers that stand out against the dark background of a pine forest. Le viaduc de Grueize, Charles Talansier, 1891, p. 146. Designed for two railroad lines, it comprises six 25-meter arches and has a total length of 218.80 m, with a maximum height of 63.30 m, measured from rail level to the lowest point in the valley. Its width between parapets is generally 8 m, but reaches 10 m at the

pier A pier is a raised structure that rises above a body of water and usually juts out from its shore, typically supported by piling, piles or column, pillars, and provides above-water access to offshore areas. Frequent pier uses include fishing, b ...

buttress A buttress is an architectural structure built against or projecting from a wall which serves to support or reinforce the wall. Buttresses are fairly common on more ancient (typically Gothic) buildings, as a means of providing support to act ...

es. The structure is straight, with a gradient of 27.5 millimetres per meter as it descends towards Marvejols. The viaduct in August 1883 Project plans Elevation_Viaduc_Crueize

Construction techniques

"The arch vaults have an

intrados An arch is a curved vertical structure spanning an open space underneath it. Arches may support the load above them, or they may perform a purely decorative role. As a decorative element, the arch dates back to the 4th millennium BC, but stru ...

composed of two quarter-circles with a radius of 12.915 m and 12.085 m, respectively. This is intended to compensate for the

gradient In vector calculus, the gradient of a scalar-valued differentiable function f of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p gives the direction and the rate of fastest increase. The g ...

while keeping the bases of two adjacent arches at the same level. This method has the advantage of bringing the resultant pressure back towards the center of the pile. These arch vaults have a thickness of 1.30 m at the keystone. The structure is refined by three longitudinal vaults, each 1.20 m wide". "The pillars show, on all sides, a progressive

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

(decrease in thickness) from the bottom to the top. This system, first used by Messrs Robaglia, Inspector General of Ponts et Chaussées, and Pader, Chief Engineer, on the Vezouillac Viaduct (currently on the section between Millau and Séverac-le-Château), has the effect of levelling the pressures on the different piers. It eliminates the protrusions (the part that forms an overhang on the vertical plane) that would have been necessary to create at different heights. By eliminating the protrusions, the edges are left in all their purity, and their continuity helps to mark the height of the structure". Nevertheless, "to facilitate the laying of the rubble stones for the edges and facing, the theoretical curve is replaced by a series of straight lines 5 m long, forming a polygon inscribed within the theoretical curve". Because of its distance, an observer at first glance sees only a regular curve. "The buttresses are set against the piers and rise up to the top of the viaduct. They are two meters wide at the base, and extend one meter beyond the

spandrel A spandrel is a roughly triangular space, usually found in pairs, between the top of an arch and a rectangular frame, between the tops of two adjacent arches, or one of the four spaces between a circle within a square. They are frequently fil ...

s at the

plinth A pedestal or plinth is a support at the bottom of a statue, vase, column, or certain altars. Smaller pedestals, especially if round in shape, may be called socles. In civil engineering, it is also called ''basement''. The minimum height o ...

. The maximum depth of the foundations is ten meters, and on average 6.50 m".

Materials used

Only the capping is in

ashlar Ashlar () is a cut and dressed rock (geology), stone, worked using a chisel to achieve a specific form, typically rectangular in shape. The term can also refer to a structure built from such stones. Ashlar is the finest stone masonry unit, a ...

. "The bands of the arches, as well as the corners of the piers, abutments, and buttresses, are in smoothed rubble, while the other visible facings are in stubbed rubble. Double chiseling is used along the edges to define the lines and ensure accuracy". The blockwork is made out of

gneiss Gneiss (pronounced ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. This rock is formed under p ...

rubble, the cladding is in sandstone and the ashlar capping stone is in

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

. The lime used comes from factories in Le Teil and

Cruas Cruas (; ) is a Communes of France, commune near the river Rhône in the Ardèche Departments of France, department in southern France. The village has a Romanesque architecture, Romanesque abbey with a crypt. Population Sights and monument ...

. The sand comes from a variety of sources: "some is extracted from the bed of the

Colagne The Colagne () is a long river in the Lozère ''departments of France, département'', southeastern France. Its source is in Arzenc-de-Randon. It flows generally southwest. It is a right tributary of the Lot (river), Lot into which it flows betwee ...

, some comes from an open quarry in deposits of ancient formation, yielding sand of superior quality, and a smaller quantity is obtained by crushing and washing soft granite supplied by a trench. Mortar for vaulted masonry is made up to 1.50 m above the joints and up to 1.50 m on either side of the keystone, by adding 200 kg of slow-setting cement per cubic meter of mortar. The three layers of cladding are finished with slow-setting

cement A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mi ...

mortar".

Centring

"The

centring Centring, centre, centering"Centering 2, Centring 2" def. 1. Whitney, William Dwight, and Benjamin E. Smith. ''The Century dictionary and cyclopedia''. vol. 2. New York: Century Co., 1901. p. 885., or center is a type of falsework: the temporary s ...

(a temporary wooden structure used for vault construction) was supported by a double row of rails running through the masonry of the piers. The first supports for the legs of the

rafter A rafter is one of a series of sloped structural members such as Beam (structure), steel beams that extend from the ridge or hip to the wall plate, downslope perimeter or eave, and that are designed to support the roof Roof shingle, shingles, ...

s were established at the level of the crossheads. Each support consisted of two rails weighing 36 kg per running meter. The second row of supports, placed four meters below, consisted of a single rail on which, via a sole plate, struts supported the main crossbeams towards the middle. These centrings were hoisted onto the upper floor of the service bridge established for the construction of the piers". Each one required 156.117 m³ of wood and 4,958 kg of iron (bolts and various reinforcements). When the centring was dismantled, the compaction of the arches was measured at 0.009 m.

Costs

The total cost of building the viaduct was 1,290,000 francs at the time, comprising 589,885.82 Fr for the piers and abutments, 527,030.21 Fr for the plinths and parapets, 19,841.17 Fr for the foundations and 63,136.23 Fr for the centrings.

Notes

References

Bibliography

* Charles Talansier, "Travaux publics : le viaduc de Crueize sur la ligne du chemin de fer de Marvéjols à Neussargues", ''Le Génie civil : revue générale des industries française & étrangères'', t. XVIII, no 10, January 2, 1891, p. 145-146
read onlinearchive
accessed January 20, 2016) * Paul Séjourné, ''Grandes voutes'', t. IV: ''Pratique des voutes, Bourges'', Imprimerie Veuve Tardy-Pigelet et Fils, 1916
read onlinearchive
, pp. 54, 58–61, 71, 83, 96, 237 * "La ligne des Causses: viaduc de la Crueize", in Jean-Luc Flohic (ed.), ''Le Patrimoine de la SNCF et des chemins de fer français'', t. I, Paris, Flohic éditions, coll. "Le patrimoine des institutions économiques", 1999 (), p. 132

External links

* Architecture resource
Structurae
*
Viaduc de la Crueizearchive
on ''Massif Central ferroviaire''. {{List of bridges in France Railway bridges in France Arch bridges in France Viaducts in France