Castielertobel Viaduct
Encyclopedia
The Castielertobel Viaduct is a single track railway bridge spanning the Castielertobelbach, and linking the municipalities of Castiel
and Calfreisen
, in the Canton
of Graubünden
, Switzerland
.
It was built between 1913 and 1914 for the Chur–Arosa railway, and is now owned and used by the Rhaetian Railway.
is located on the Rhaetian Railway's metre gauge
line from Chur
to the holiday and recreation resort of Arosa
(the Chur–Arosa line), and links Calfreisen with Castiel, just to the west of the Lüen-Castiel railway station
.
After the Langwieser Viaduct
and the Gründjitobel Viaduct
, the Castielertobel Viaduct is the third largest bridge on the Arosa line. It spans the Castielertobel, a wild and deeply eroded Bündner schist gorge, and the Castielertobelbach. In similar fashion to the Landwasser Viaduct
on the Rhaetian Railway's Albula Railway
, the viaduct leads directly into a tunnel portal, where the Arosa line dives into the 249 m long S-shaped Bärenfalle-Tunnel.
Like most of the other bridges on the line, the Castielertobel Viaduct was constructed in the classical manner, and mainly of stone. However, the special site conditions dictated the inclusion of stampfbeton (unreinforced concrete compressed by stamping) in the cores of the stone pillars.
In light of the spectacular, and topographically extremely difficult, rises and falls of the Castielertobel (the so-called Bärenfalle, or bear traps, which, despite being relatively close to the nearby cantonal road, were almost unknown before the Arosa line was constructed), the engineers had to resort to using fire and smoke signal
s to help them survey the line's route. During construction of the viaduct, access was provided to the construction site from Sassal via Calfreisertobel, on makeshift tracks laid over the already completed railway formation. Horses pulled the necessary materials to the construction site on transporter wagon
s.
The construction of the Bärenfalle-Tunnel was begun from Eichwald, uphill from Castiel. The tunnel constructors made their breakthrough while both of the viaduct's pillars were still under construction.
Despite the viaduct's construction challenges, the viaduct building process itself was surprisingly trouble free: although the main pillars were begun only in April 1913, the whole viaduct, including its deck, was complete by November of the same year. By contrast, a potential rock fall at the uphill portal of the Bärenfalle-Tunnel threatened to block passage through the tunnel just at the moment when transport of machinery to the Lüen
power station
was due to begin.
In 1931, following many observations and detailed investigations, work therefore began on an initial reconstruction of the viaduct. The work was carried out by the firm B. & C. Caprez. During that work, the valley side abutment was underpinned by a bell-shaped concrete block, which was clad with Hunziker stones, and reinforced with rails. The block had a diameter of 14 metres (45.9 ft) and a height of 9 metres (29.5 ft). Additionally, a new foundation base was laid some 21 metres (68.9 ft) below the previous ground level.
It soon turned out that these measures were not sufficient. In 1942, the entire bridge structure was therefore rebuilt. All three of the stone arches were removed and replaced by iron girders, to overcome the viaduct's previous vulnerability to landslides and associated deformations. Installation of underlying "fish-bellied" girders maximised stability. Chief engineer Hans Conrad headed up this startling transformation, without any need for the railway operations to be interrupted.
Since the completion of the 1942 reconstruction, its special design has compensated for slipping movements, which cannot be eliminated, even by modern engineering measures. Both piers of the viaduct are regularly reviewed to detect irregularities immediately. A monitoring device attached to the viaduct makes it possible to register even the slightest shifts. Additionally, a 7 tonnes (6.9 LT) counterweight suspended from a wire rope provides a 50 tonnes (49.2 LT) pulling effect on the pier heads, along the line of the railway formation towards Chur.
Castiel
Castiel is a municipality in the district of Plessur in the canton of Graubünden in Switzerland.-Geography:Castiel has an area, , of . Of this area, 43.1% is used for agricultural purposes, while 49.2% is forested...
and Calfreisen
Calfreisen
Calfreisen is a municipality in the district of Plessur in the canton of Graubünden in Switzerland.-Geography:Calfreisen has an area, , of . Of this area, 49.5% is used for agricultural purposes, while 30% is forested...
, in the Canton
Cantons of Switzerland
The 26 cantons of Switzerland are the member states of the federal state of Switzerland. Each canton was a fully sovereign state with its own borders, army and currency from the Treaty of Westphalia until the establishment of the Swiss federal state in 1848...
of Graubünden
Graubünden
Graubünden or Grisons is the largest and easternmost canton of Switzerland. The canton shares borders with the cantons of Ticino, Uri, Glarus and St. Gallen and international borders with Italy, Austria and Liechtenstein...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
.
It was built between 1913 and 1914 for the Chur–Arosa railway, and is now owned and used by the Rhaetian Railway.
Location
The viaductViaduct
A viaduct is a bridge composed of several small spans. The term viaduct is derived from the Latin via for road and ducere to lead something. However, the Ancient Romans did not use that term per se; it is a modern derivation from an analogy with aqueduct. Like the Roman aqueducts, many early...
is located on the Rhaetian Railway's metre gauge
Metre gauge
Metre gauge refers to narrow gauge railways and tramways with a track gauge of . In some African, American and Asian countries it is the main gauge. In Europe it has been used for local railways in France, Germany, and Belgium, most of which were closed down in mid 20th century. Only in Switzerland...
line from Chur
Chur railway station
Chur railway station serves the city of Chur, capital of the Canton of Graubünden, Switzerland. Opened in 1858, it is the most important railway junction in Graubünden....
to the holiday and recreation resort of Arosa
Arosa (Rhaetian Railway station)
Arosa is a railway station on the Chur-Arosa line of the Rhaetian Railway . It is situated in the town and resort of Arosa, close by to the Obersee ....
(the Chur–Arosa line), and links Calfreisen with Castiel, just to the west of the Lüen-Castiel railway station
Lüen-Castiel (Rhaetian Railway station)
Lüen-Castiel is a railway station on the Chur-Arosa line of the Rhaetian Railway . It is situated in Lüen and also serves nearby Castiel....
.
After the Langwieser Viaduct
Langwieser Viaduct
The Langwieser Viaduct is a single track reinforced concrete railway bridge spanning the Plessur River and the Sapünerbach, near Langwies, in the Canton of Graubünden, Switzerland....
and the Gründjitobel Viaduct
Gründjitobel Viaduct
The Gründjitobel Viaduct is a single track reinforced concrete railway bridge, spanning the Gründjitobelbach near Langwies, in the Canton of Graubünden, Switzerland....
, the Castielertobel Viaduct is the third largest bridge on the Arosa line. It spans the Castielertobel, a wild and deeply eroded Bündner schist gorge, and the Castielertobelbach. In similar fashion to the Landwasser Viaduct
Landwasser Viaduct
The Landwasser Viaduct is a single track six-arched curved limestone railway viaduct. It spans the Landwasser River between Schmitten and Filisur, in the Canton of Graubünden, Switzerland....
on the Rhaetian Railway's Albula Railway
Albula Railway
In 1890, the Davos hotelier Willem-Jan Holsboer proposed the construction of a rail link from Chur via Davos, and through a tunnel under the Scaletta Pass, to St Moritz, and then onwards via the Maloja Pass, to Chiavenna in Italy. Holsboer later had to abandon this planned Scalettabahn, in favour...
, the viaduct leads directly into a tunnel portal, where the Arosa line dives into the 249 m long S-shaped Bärenfalle-Tunnel.
The original stone bridge
Due to the difficult geological conditions in the Schanfigg valley, a total of 18 tunnels and 40 bridges needed to be created between 1912 and 1914 for the privately built Arosa line.Like most of the other bridges on the line, the Castielertobel Viaduct was constructed in the classical manner, and mainly of stone. However, the special site conditions dictated the inclusion of stampfbeton (unreinforced concrete compressed by stamping) in the cores of the stone pillars.
In light of the spectacular, and topographically extremely difficult, rises and falls of the Castielertobel (the so-called Bärenfalle, or bear traps, which, despite being relatively close to the nearby cantonal road, were almost unknown before the Arosa line was constructed), the engineers had to resort to using fire and smoke signal
Smoke signal
The smoke signal is one of the oldest forms of communication in recorded history. It is a form of visual communication used over long distance.-History and usage:...
s to help them survey the line's route. During construction of the viaduct, access was provided to the construction site from Sassal via Calfreisertobel, on makeshift tracks laid over the already completed railway formation. Horses pulled the necessary materials to the construction site on transporter wagon
Transporter wagon
A transporter wagon, in railway terminology, is a wagon or railroad car designed to carry other railway equipment. Normally, it is used to transport equipment of a different rail gauge...
s.
The construction of the Bärenfalle-Tunnel was begun from Eichwald, uphill from Castiel. The tunnel constructors made their breakthrough while both of the viaduct's pillars were still under construction.
Despite the viaduct's construction challenges, the viaduct building process itself was surprisingly trouble free: although the main pillars were begun only in April 1913, the whole viaduct, including its deck, was complete by November of the same year. By contrast, a potential rock fall at the uphill portal of the Bärenfalle-Tunnel threatened to block passage through the tunnel just at the moment when transport of machinery to the Lüen
Lüen
Lüen is a municipality in the district of Plessur in the canton of Graubünden in Switzerland.-Geography:Lüen has an area, , of . Of this area, 37% is used for agricultural purposes, while 52.3% is forested...
power station
Power station
A power station is an industrial facility for the generation of electric energy....
was due to begin.
Stabilisation and reconstruction measures
The site conditions soon proved to be very unfavorable to the completed viaduct, with the result that the 53 metres (173.9 ft) high main pillars slipped each year by about 6 millimetre (0.236220472440945 in) downstream towards the Plessur River. Relatively quickly, this led to considerable deformation of the vaulting.In 1931, following many observations and detailed investigations, work therefore began on an initial reconstruction of the viaduct. The work was carried out by the firm B. & C. Caprez. During that work, the valley side abutment was underpinned by a bell-shaped concrete block, which was clad with Hunziker stones, and reinforced with rails. The block had a diameter of 14 metres (45.9 ft) and a height of 9 metres (29.5 ft). Additionally, a new foundation base was laid some 21 metres (68.9 ft) below the previous ground level.
It soon turned out that these measures were not sufficient. In 1942, the entire bridge structure was therefore rebuilt. All three of the stone arches were removed and replaced by iron girders, to overcome the viaduct's previous vulnerability to landslides and associated deformations. Installation of underlying "fish-bellied" girders maximised stability. Chief engineer Hans Conrad headed up this startling transformation, without any need for the railway operations to be interrupted.
Since the completion of the 1942 reconstruction, its special design has compensated for slipping movements, which cannot be eliminated, even by modern engineering measures. Both piers of the viaduct are regularly reviewed to detect irregularities immediately. A monitoring device attached to the viaduct makes it possible to register even the slightest shifts. Additionally, a 7 tonnes (6.9 LT) counterweight suspended from a wire rope provides a 50 tonnes (49.2 LT) pulling effect on the pier heads, along the line of the railway formation towards Chur.
Technical data
The Castielertobel Viaduct is 115 metres (377.3 ft) long. Its main span is 25 metres (82 ft) long, and has a rise of 53 metres (173.9 ft). The viaduct has a total of three spans.See also
- Arch bridgeArch bridgeAn arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side...
- Truss bridgeTruss bridgeA truss bridge is a bridge composed of connected elements which may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges...
- ViaductViaductA viaduct is a bridge composed of several small spans. The term viaduct is derived from the Latin via for road and ducere to lead something. However, the Ancient Romans did not use that term per se; it is a modern derivation from an analogy with aqueduct. Like the Roman aqueducts, many early...
- Lüen-Castiel (Rhaetian Railway station)Lüen-Castiel (Rhaetian Railway station)Lüen-Castiel is a railway station on the Chur-Arosa line of the Rhaetian Railway . It is situated in Lüen and also serves nearby Castiel....
- Gründjitobel ViaductGründjitobel ViaductThe Gründjitobel Viaduct is a single track reinforced concrete railway bridge, spanning the Gründjitobelbach near Langwies, in the Canton of Graubünden, Switzerland....
- Langwieser ViaductLangwieser ViaductThe Langwieser Viaduct is a single track reinforced concrete railway bridge spanning the Plessur River and the Sapünerbach, near Langwies, in the Canton of Graubünden, Switzerland....
- Chur–Arosa railway
- Rhaetian Railway